Yeah, this is a weird phenomenon, and I do that a lot, too (point out differences in definitions), and it irritates people sometimes. So most people refrain from pointing it out too much, like it’s taboo or something, but I don’t refrain, because it very often is the key to the whole debate. And even if it is not the big key, the debate certainly cannot even start until people agree on definitions. But it’s like deja vu, where the discussants at some point a few pages into the thread finally realize they had different definitions and resolve things, but then in the next thread it happens again with a different set of key words, and they go through the same process, thread after thread. It seems to take many exposures for most people to see the pattern, to the point where they finally learn to stay on the lookout for definitional differences from the very beginning.
The most insane thing is that if you point out semantic issues like this, people will often accuse you of “arguing semantics,” which is actually exactly what you’re trying to point out that they are doing! It’s yet another equivocation: “arguing semantics”=manipulating semantics to try to make a false argument look right (what they’re doing), vs. “arguing semantics”=making points about the semantics of the argument (what you’re doing). What a mess it becomes, when you point out an equivocation, they are blinded from seeing it by another equivocation.
Side thought: Someone said something like, “Label me, and you delete me.” It’s like people don’t want to part with their pet definitions, because by giving something a label they can put it in a box and feel like it’s a known quantity, not as scary, etc. Maybe people get irritated because you threaten to take that away from them when you remind them that definitions are arbitrary (OK, not quite totally arbitrary, but only non-arbitrary in the sense that a certain definition might be really common).