The examples seem relevant to me because they illustrate that language is not used only to predict, that the merits of a particular language-using strategy are not determined only by its impact on predictive accuracy. If language in general has proper goals other than predictive accuracy, why should I think that category-boundary drawing has no proper goal other than predictive accuracy?

I'm not sure exactly what distinction you're appealing to, by the way. In particular, you say "the communicative function of proper names ... the cognitive function of categories" and it's not clear to me whether (1) you're suggesting that proper names are used primarily for communication while categories are used primarily for cognition, or (2) you're saying that your complaints about talk of arbitrariness apply only when thinking about cognition as opposed to communication, or (3) something entirely different. I say that proper names and category boundaries are highly relevant to both communication and cognition, and that some of the examples that apparently bother you most seem much more about communication than about cognition (e.g., being asked to use pronouns that you find inappropriate for the people they refer to, which you say amounts to asking you to lie, clearly a communicative category more than a cognitive one). It's entirely possible that your meaning is something entirely different, of course; please feel free to enlighten me if so.

The pouncing algorithm can't literally be "pounce when people say nice things about TCWMFM" because in the particular case that sparked this particular discussion that didn't happen but you still pounced.

It probably won't surprise you that I don't agree with your description of TCWMFM as pants-on-fire mendacious, and I don't think the edit at the end undermines the foregoing material nearly as much as you say it does. There are rules, but the rules are of the form "if you want your thinking to be optimal in such-and-such a way, you have to think like this" and Scott is talking about words: how to speak, not how to think. Words and thoughts are closely related but they aren't the same, and I agree with Scott that neither rationality nor rationalism includes any obligation to optimize your words for the exact same thing as your thoughts.

For example, suppose that (1) someone decides to use the word "woman" to mean, as precisely as they are able, "adult human being who identifies as female", and that also (2) you are correct in holding that the region of person-space picked out by this definition is less useful for making predictions than one like "person whose gender-related characteristics are, collectively, more like those of the average woman than like those of the average man". (That definition is kinda-circular but in a way that does no actual harm, and it leaves open the question of what "more like" means, but let's suppose that (3) no plausible way of making "more like" concrete gives you anything close to "adult human who identifies as female", though I'm not sure that's actually the case.) Is our hypothetical person doing something rationalists should be ashamed to do?

I claim they need not be. They are (given all the stipulations in the previous paragraph) using language in a way that isn't optimized for prediction, but I see no reason why language-use should be optimized purely for prediction, because the actual uses of language are broader than that.

You might object that they are impairing their ability to think clearly: when they say or hear that someone is a woman, that will lead to certain expectations in their mind, and if they define "woman" in a gerrymandered way then those expectations will be wronger-in-expectation than they need be. It seems to me that any such effect is very small; someone using the word "woman" this way knows that they are doing so, knows that when someone else says "X is a woman" they don't necessarily mean it the same way, can when it seems appropriate think explicitly in terms of Y-chromosomes or hormones or whatever other characteristics might be relevant. The last point is important. When you have some category without a standard precise technical definition, and it's actually important to reason about its members, it usually turns out that what really matters isn't membership in the category as such but something more specific. Is So-and-So "really" a woman? In cases where there's any scope for doubt about that, you will get more useful answers by figuring out what the real question is (do I want to have sex with her? should I let her into my javelin-throwing competition? which public toilet should she be using? what dose of this drug should I give her? is it possible that she's pregnant? etc., etc., etc.) and answering that more directly. So, anyway, I think any thought-impairment here is very small, and reiterate that language has purposes other than facilitating clear thought; if our hypothetical person thinks there are other benefits that outweigh any such loss, it is far from obvious that they're wrong.

You might object that if they use language that way they are failing to communicate maximally informatively: if someone who uses "woman" that way tells you someone is a woman, the information they're giving you is less useful for your prediction-making than if they used the word in a prediction-optimized way. Well, maybe, kinda, but for at least two reasons I don't think this is something it's reasonable to get upset about. 1. Regardless of what they do, the word "woman" is going to have ambiguities around the edges unless the person using that word tells you explicitly and in detail where they draw the boundaries. (The same is true, in less politically-sensitive ways, of many other words. If I call something a mountain or a town, or say someone is stupid or beautiful, or say that a wall is painted green, you don't know exactly how "towns" shade into "villages" and "cities" for me, or what features make someone more beautiful or how "beautiful" shades into weaker terms like "pretty" or "sexy" or "elegant", or how I categorize turquoise-ish colours.) So even if I choose to use the word "woman" in a way that is in fact optimized for your predictive purposes, that's only any use if I first of all tell you exactly how I'm defining that word. Which almost never happens. 2. If I do tell you exactly how I'm defining the word, then no matter what definition I'm using my uses of "woman" are thereafter strictly more informative than if I don't give you that information; i.e., strictly more informative than say 99.9% of uses of the word; I don't think you're then entitled to complain that I could be helping you even more.

None of this is particularly specific to the word "woman". The same is true of, say, the word "fish" as in Scott's initial example. I think Scott is exactly correct when he says that "in no case can an agreed-upon set of borders or a category boundary be factually incorrect". Even though a category boundary absolutely can be not optimized for any reasonable notion of optimal prediction. (And can be bad in other ways; in practice, I think being very different from other people's boundaries is a more important failure mode for the purpose of communication.)

I should maybe add that I don't actually find the stipulations above very plausible. Most social interactions are rather shallow, which means that most gender-related predictions I need to make that might be influenced by what pronoun is being used for a given person have little to do with the fascinating ways in which typical men's and women's bodies or minds differ, which means that if all I know about someone is that they were referred to as "she" or that someone called them a "woman", quite possibly the most useful information I can get from that does concern whether that person would prefer to be treated as male or female. If at some point those other deeper questions start mattering to me, almost certainly by that point I will have met them, seen what they look like, talked to them, etc., and at that point most of the information I have about their personality and preferences and so forth doesn't come from their Official Gender at all. In which case, during the period when their Official Gender is actually of much use for my predictions, the predictions I'm needing to make are in fact mostly about "how they identify".

I consider this evidence in favor of 'keeping politics out of lesswrong does help with 'rationality''.

Sorry, I'm not following the reasoning here; can you say more? Why that specific hypothesis, rather than "ZMD's writing is too long-winded in general"?