I could use a better name for this (any suggestions?), but I'll use "distinctions of the moment" for the moment.
A distinction of the moment is a distinction made between two synonyms or near-synonyms (or sometimes antonyms), for the sake of pointing out a difference which is important to the discussion at hand. For example, I might contrast "knowledge" and "understanding" for the sake of a discussion about memorization-and-regurgitation style education vs focusing more on reasons. In a different conversation, I may well use "knowledge" vs "understanding" to talk about knowing-how vs knowing-what (and I might well call either of those two "understanding" and the other "knowledge" -- it doesn't matter, it's just a distinction of the moment).
The important thing about distinctions of the moment is that they just have to be made clear for the purpose of the conversation, and can be thrown away afterwards. This fails if someone thinks that they need to argue the definition of a word as if it were a sacred duty. Perhaps I make a distinction between "liberal" and "progressive" for the purpose of conversation, and someone takes issue with it because they've got a favorite definition of one or both of those terms which they think is importantly correct. This is not useful to the conversation.
A pet peeve of mine is that a lot of people seem to carry around distinctions-of-the-moment forever, as if they were true subtle differences in the meanings of words. I feel this way about distinguishing between "sympathy" and "empathy" -- I'm not sure quite why, but it seems to me that the distinction people tend to draw between the two is something which is just not generally useful enough to be more than a distinction-of-the-moment. The two words have different usage patterns, yes, but I don't think those usage patterns are really well-explained by "feeling emotion in response to others vs putting yourself in their shoes".
The words that came to mind here were "label" and "handle," but I think the longer phrase "distinction of the moment" is clearer (though longer).
This seems like it's using "true subtle differences" as being a property of the territory instead of the map, which worries me somewhat. An old analogy here is something like a fuel injector and an intake manifold--to a layman, they're just 'car parts', whereas to a mechanic, they're clearly distinct. There are word pairs where there are distinctions that seem unimportant to me (less vs. fewer, comprise vs. compose, etc.) and then other where they do seem important to me (a marginal case on this side of the divide is that vs. which), and if someone is conflating the two it seems like to right move is to complain "hey, I was using that distinction!"
Yeah, I don't think I've successfully drawn a line around the cases which annoy me. Here are some of the things that come to mind:
The words really are near-synonyms.
The definition offered doesn't fit the usage, even of the person offering the definition. I think the sympathy/empathy example illustrates this; lots of people will give a verbal explanation of the difference between the two, but it seems only shallowly based on usage differences, if at all.
The definitions offered are claimed to be general, rather than special case (which, especially in combination with the previous point, makes me tend to think that the person doesn't know how words work -- or at least, makes me think they aren't a person who is aware of how words can fluidly adapt to the needs of the conversation).
The distinction being offered isn't particularly crafted to fit the situation. (I may develop a suspicion that the person is mentioning the distinction just to sound smart -- something which might not annoy me in other contexts, but does annoy me when I identify it as a mis-used distinction-of-the-moment.)
The distinction offered doesn't strike me as particularly generally useful. I'll forgive all the previous points if someone is giving a distinction which I find illuminating.