There are some things which it's impolite to say, in any words, because the sentiment is impolite--for example, "I don't want you to come to my party." Guess culture, applied well, allows you to avoid having to say those things or cause the attendant hurt feelings. (Guess culture applied poorly avoids the hurt feelings but puts you in the awkward position where they're at the party anyway because you felt compelled to invite them.) The same situation in ask culture requires you come out with it.

This may sound like a good thing in the long run--especially if you are yourself asky--but sometimes there are valid reasons both that you don't want someone at the party (they smell bad) and that you don't want to hurt their feelings (they're your boss/family member/other person you'll be spending more time around, especially in a position of authority).

Another thing guess culture is good at is keeping secrets. In ask culture, if someone asks you something you've promised not to tell, it's certainly valid to say "Sorry, I can't tell you." But then they know there's a secret, and sometimes that alone is enough to cause harm--through speculation and deduction, or asking someone else, for example. (You could also lie, but that might cause its own problems.) In guess culture, there are things you don't ask about. This is part of why.

FWIW, among my friends--whom I might describe as "polite askers" or "assertive guessers"--it's common to ask "does anybody want to split this with me?" That way, you're both asking for what you want (more of the thing) and making an offer in a guess-culture-compatible way. It's easy for other people to accept, because now by taking it they're not preventing you from having it. If no one does, you can be reasonably confident no one else actually wanted it.

A variant on the same thing is: "Would anyone else like this?" which is a shorter version of the offering ritual that TheOtherDave described. Because it's skipping most of the ceremony, it's much askier, but it's still not polite to say "yes" and take the thing, because you'd be taking it out of the hands of someone who clearly wanted it. (An exception might be made if you hadn't actually had any of the thing yet, and said so.) But you can say "I'll split it with you," achieving the same result as the above.

Of course, this only works for plausibly divisible things. I've had a friend laugh at me--good-naturedly--for offering to split something bite-sized. Surprise, surprise: he's much askier, I'm much guessier.

Correction: it's a good excuse to eat TWICE as much pie.

thanking-for-thanking, long buildups to requests, apologising for things which are clearly not the other persons' fault

(Assuming you mean "not the apologizer's fault" in the last one.) I don't do these things, and I don't think they're necessary forms of courtesy, at least in a peer situation--customer service calls for jumping through hoops sometimes but I don't think that's what we're discussing.

How much have you considered the level of politeness you prefer to receive as opposed to the potentially interesting/fun problem of working out what to transmit?

I suspect that I'm similar to most people in that I notice mostly when someone uses a politeness level which is not what I wanted. ;) I'm not sure what terms I could use to clarify what that level is, though.

Yeah, but the scale we're using isn't very precise. The variables you mention will move the threshold around, certainly, but not so much that shokwave can't at least give me a smallish range. We can limit it to modern, Western, and no significant status differences from each other.

Polite means a very different thing here (Australia) than it does in the US for example.

Yeah, I can tell. ;)

In actual practice I behave the way I described; I like to think that if this were drastically counterproductive for my goals, I would have noticed by now.

At any rate, the goal under discussion was informing the other person of the error in a way that didn't result in defensiveness or aggression.

Oh, interesting. I hadn't thought of it in those terms before but it does immediately make sense.

It's true about status, though. It works out okay in my current time and place, where I very rarely encounter people whose status is so drastically and publicly different from mine that it would call for significantly different behavior. Or at least, that's my perception; if I encountered one of your friends on the other side of a cash register, we'd apparently have different ideas about what our relative status was and what level of courtesy was called for. I wonder what leads to that difference.

Hmm. I think you're onto something, but that doesn't quite fit for me. Off the top of my head, I think I do something more like this:

I run the words I'm considering saying through my mental simulation of the person I'm talking to--which is going to have "like me" or "like normal" as defaults where I lack details--and check for snags like "does not acknowledge hearer's agency/competence" or "implies hearer smells bad." If I find one, I'll either remove/change the problematic wording or add words to counterbalance them.

Of course, as I get better at it, I also improve a lower-level filter on "things to not say at all," like giving advice to people in any situation where I don't actually have more knowledge or experience than they do. That's another kettle of worms, though.

The difference between that and your model of me is that it's also a multi-stage process; it's just fast. It may bear noting that I find it really interesting how much small word choices affect implication and connotation, which probably helps a lot with not being frustrated by the task. It's work, but it's fun work--like a productive debugging session.

The difference between the above and your model of you is that rather than taking a concept and adding semantically null politeness indicators around it, I'm making small adjustments to the presentation of the concept.

We may not actually be doing or imagining such different things, but I think that difference in our perception of the task is very telling. Your second model definitely lends itself to descriptors like "fluff" and "inefficient" and "time-consuming," whereas even in cases where it actually is noticeably time-consuming, the model I described above feels much more like an intellectual puzzle.

But then the question becomes: is it our different models of the mental process of diplomacy which causes us to have different feelings about it, or is it the other way around? The former seems like it would be easy to change in one's own mind, if one wanted; the latter puts us back where we started.

Something else I notice on rereading my description is that my model depends on having fairly reliable simulations of listeners, and fairly robust defaults when a specific data is not available. I expect that being able to build those simulations is an improveable skill. Empathy is a good head start on it, but one can care enough to try and still not have enough practice to do it well. As for the defaults: as I mentioned, I'll use myself when I don't know any better, and the accuracy of doing so would logically correlate to neurotypicality and otherwise being more like more potential listeners.

Summary: More agreeable models of what diplomacy requires may lead to more agreeable feelings about it, or vice versa. Some skills which make it easier can probably be learned; being empathetic and being neurotypical probably give you a leg up. Nothing earth-shaking, but an interesting puzzle nonetheless.

Hmm. Getting an answer forced me to figure out exactly why I was asking. ;) I guess the followup question is, where on that scale would you put the threshold for everyday, out-in-public polite conversation between neurotypical adults? That is, the expected level, below which someone would come across as rude.

Well, that's as much politeness as I was talking about, so I still think it's no worse than bluntness would have been.