I had a super-long Okcupid profile up for about seven years minus the <1y period where I was in a relationship with someone I met irl via EA/work. I also had tinder for a period of time, where I circumvented the word limit by linking to text from my Okcupid profile. I always thought the long profile was the right approach for me because I knew that people who are soulmate-compatible with me would appreciate both the length and the honesty.

I was primarily looking for a life-long relationship, but there were times where I noted that I'd be interested in trying out more casual relationships while the search was continuing. (This was certainly a tradeoff: the long-profile approach is probably suboptimal for impressing women who are looking for a more casual relationship.)

After seven years of very little success, someone replied to me with "I've just read your profile and I have rarely come across someone so like-minded, ever. It's a little bit uncanny." It turned out that this impression of uncanny compatibility was mutual! We've been together for nearly 1.5 years now and things couldn't be better<3

So, it was definitely worth it for me, even though it seemed like the profile wasn't doing much for me for the vast majority of the time that I had it. (For instance, even on the rare occasions where I got replies to first messages, it would almost never lead to a conversation where the women would eventually comment on the parts of my profile that I was particularly fond of.) 

When it comes to online dating, it can be very useful to really think about the properties of the medium you are using.

There was a time when Tinder ran on ELO score. That means if all the people that you like also liked you back, you were shown to a lot of people. Practically, that could be gamed by getting Tinder Gold and only swiping right on partners that already matched with you. A friend of mine who is also a dating coach said that at the time he had a week where he had three dates via online dating per day. 

This means that if you ask a question such as whether long-form dating profiles are productive, it makes sense to focus on the medium in which you would write them. 

I remember one rationalist who made a fermi estimate according to which there are likely around 500 women in the world who fit the criteria of what he's looking for. He then thought about how to find one of those as his partner and went to work. He found one of the women who fit his criteria and is now happily married since 2017.

If you write a dating profile outside of a dating website you might limit the number of people who see it, but at the same time, you might still get the people you actually care about to see it.  

Community-wise long-form dating profiles make it easier for other community members to help with match-making. This is especially true in our community. It's socially awkward for a lot of people to suggest that two people in the community who are single should date. It's a lot less awkward to tell somebody: "Hey, I think you match what X is looking for and wrote in her long-form dating profile". At https://www.facebook.com/groups/898553654177315/ there seems to be the intention to make this even more efficient by putting up match-making bounties. 

A profile that's written to make the job of match-makers easy is likely a very different one that's written for OkCupid. For OkCupid, it's very important that the profile hooks the reader into reading it and makes them feel emotions while reading it. The infodump for rational matchmaking on the other hand is usually in a very fact-driven style. As an audience rationalists are likely also care more about evaluating the information. 

Caveat: I don't know what is this manual distribution method you're talking about, so I'll address the essence regardless of what technology is used to implement it. That is, I'm interpreting "long profile" as "lots of text in your profile or linked from it".

Most people write barely anything in their profile and (I guess??) care more about the photos more than the text in other profiles. However, I don't want to date most people. The mindset of choosing people to date primarily based on the photo seems to me, frankly, almost alien. They do them, but I'm not gonna do them. If I see a profile without substantial information about interests, worldview or personality, which is not completely shallow and generic, there's no chance I would be interested.

In practice, I met my spouse on OK Cupid. We both wrote a lot in our profiles, and answered a tonne of questions (99% compatibility). This is not a coincidence! So, my advice is: imagine the kind of person you want to date. Is this person going to be mostly interested in your looks? Or, they will care deeply about you-the-person and what makes you different from any other random person out there? If it's the former, don't write a long profile. If it's the latter, then obviously you do want a long profile.

Epistemic status: intuition and some experience, no sources.

Long-form profiles are mostly a waste of time. The two key weaknesses are 1) the primacy of photos and 2) adversarial communication

1. Tinder made millions by realizing that many, many users make snap decisions based on photos and the rest doesn't produce as strong of results. That's not to say no one reads the profiles and decides on them, but at least a minority do (and some will just stay anchored to their impression of the photos while reading anyways).

2. Dating is a "lemon market," where everyone playing wants to attract the highest-quality partner they can relative to their own status. That means when you write a long-form profile, you're incentivized to fluff it up and present yourself in the best possible light, and when you're reading a profile you need to take that into account when trying to evaluate quality. And even if you're honest, other readers will probably still apply the critical lens. This doesn't degrade the value of the long-form profile signal to zero, but it does discount the return on your time investment.

Now that I'm happily engaged I tend to think my pessimism on the value of online dating full stop was well-warranted and there's no substitute for in-person socializing, particularly in a group/community space where the adversarial presentation dynamics are reduced. If my current mind was thrown back in time to when I was 18 I'd skip online dating altogether and just get into more clubs and study groups and stuff in college.

Writing my dating profile was a good use of my time before I shared it with anybody. I had an insufficiently strong sense of what kind of relationship I want and why other people might want to have it with me. The exercise of "make a freeform document capturing all of that" was very helpful for focusing my mind towards figuring it out -- much moreso than the exercise of "fill in dating app textboxes in a way that seems competitive for the swiping game". (This is just a special case of "writing an essay teaches you a lot" -- something I'd like to take advantage of more often)

It took about 1 workday of writing effort to put mine together, and it's resulted in 2 high-quality dates (order of 10k micromarriages) in the past 5 months. This is competitive with the rest of my current tools for turning effort into dating prospects. 

They have the benefit of being slightly costly signals, requiring significantly more time and attention and a much greater degree of disclosure than can be devoted to a traditional online dating profile

This feels like a very cynical view of dating docs. The advantage is that they give you a lot more space to share a lot more detail. 

It's still valid to ask if they work, but if you're viewing it all as signalling and disclosure you're missing the actual upside. 

I'm extremely morally reluctant to date anyone. I feel like neither side could be completely genuine. I have no problem being single for the rest of my life, but for the sake of my own health, especially in later life, I feel I should at least give it a chance to see if relationship would work out with the only person I've had a relationship with in the past. If it does, then we will be both better off in terms of health in later life. If not, then I will still be single, but this time, hopefully I will be wise enough to avoid running into significant trauma that might end up making my life worse.

Productive for what, exactly? There's a lot of assumed context missing from the post, including your gender, and the gender you're targeting. It's also not completely clear what kind of relationship you want, but we'll assume it's serious and long-term.

First: you're XY, looking for XX. In this case, @swarriner's post is applicable to most of the distribution. But since you're here, we'll assume the girl you're looking for is intellectually gifted, data oriented, and may or may not be slightly on the spectrum. Even in this case, pictures are still worth 1000 words, but a lengthy profile probably won't hurt (it may not help that much, though.) If you're going for someone in the bulk of the distribution, a long profile will most likely hurt, not help. In short, make sure you have good pictures, and don't rely on your own judgement or that of biased parties to assess whether the pictures are good.

Second: You're XY looking for XY. In this case a long profile is probably pretty useful, but your pictures still need to be good.

Third: NB for one, the other or both. In this case a long description is probably generally useful. Don't know enough about this case. 

Fourth: You're XX looking for anything. A long profile isn't necessary, just some pictures and a short signal that you're smart and nerdy. The pictures don't need to be that good. 

edit: what went wrong here? why is this controversial? anyone can explain? 

Online dating is fundamentally asymmetric as there are more than twice as many men than there are fertile age women. With long form dating profiles, men are at real risk of appearing weak. Women are more likely to respond to brief profiles that make a man look strong and capable.