Ok, so let's say I've determined that I want to have fun. I conclude from this that I should play in such a way as to make me have the most fun. What now? How does this help me?
This isn't the situation we're talking about, though, we're talking about you advising someone how to better complete the game's intended goals when they already know that they'd prefer to play less conventionally. In that case, it helps them because it tells them to not follow your advice because it would reduce the amount of fun they have.
clarify something for me, please: are you disputing that the conditional statement is true? If so, why? If not, what is your objection?
No, I'm not disputing that the conditional is true. My objection is that your top comment doesn't clarify what "playing effectively" means, and it seems that you think that players placing a value on personalization is wrong because it makes them less effective. It sounds like a case of Lost Purposes. You find out that someone's gameplay preferences are different from those of "optimal play", and you consider that a problem instead of an equally valid taste.
we're talking about you advising someone how to better complete the game's intended goals when they already know that they'd prefer to play less conventionally
Where are you getting this? (The italicized part especially is something that is, as far as I can tell, untrue of the situations I am describing.)
and it seems that you think that players placing a value on personalization is wrong because it makes them less effective
This directly contradicts what I said here:
...If your fun depends on doing things other than accomplishing the goals presented to
There are things that are worthless-- that provide no value. There are also things that are worse than worthless-- things that provide negative value. I have found that people sometimes confuse the latter for the former, which can carry potentially dire consequences.
One simple example of this is in fencing. I once fenced with an opponent who put a bit of an unnecessary twirl on his blade when recovering from each parry. After our bout, one of the spectators pointed out that there wasn't any point to the twirls and that my opponent would improve by simply not doing them anymore. My opponent claimed that, even if the twirls were unnecessary, at worst they were merely an aesthetic preference that was useless but not actually harmful.
However, the observer explained that any unnecessary movement is harmful in fencing, because it spends time and energy that could be put to better use-- even if that use is just recovering a split second faster! [1]
During our bout, I indeed scored at least one touch because my opponent's twirling recovery was slower than a less flashy standard movement. That touch could well be the difference between victory and defeat; in a real sword fight, it could be the difference between life and death.
This isn't, of course, to say that everything unnecessary is damaging. There are many things that we can simply be indifferent towards. If I am about to go and fence a bout, the color of the shirt that I wear under my jacket is of no concern to me-- but if I had spent significant time before the bout debating over what shirt to wear instead of training, it would become a damaging detail rather than a meaningless one.
In other words, the real damage is dealt when something is not only unnecessary, but consumes resources that could instead be used for productive tasks. We see this relatively easily when it comes to matters of money, but when it comes to wastes of time and effort, many fail to make the inductive leap.
[1] Miyamoto Musashi agrees: