Pedantry is an inherent part of nerd-dom. It's often a good thing. Computers and other such things don't work on "well, you know what I
meant".
However, there's a nasty subset of pedantry which basically consists of pattern-matching words without truly grasping the meaning and using that as a launching point for a "you're wrong" reply. This kind of pedantry derails conversations and wrecks communities.
That's the kind of pedantry I got above with this nonsense reply about how "in metric they would use liters". As if I didn't know that! A moment's thought would indicate, hey, maybe this guy is not a complete idiot who doesn't know anything about metric, and he probably already knows that neither ounces nor gallons are metric, so let's figure out what he actually meant instead of doing a mindless pattern-matching "you're wrong" reply. That is hostility too. Especially when you keep on going even after the guy explains it.
And of course I get the usual internet double standard, where it's perfectly OK to to write a really bad comment as long as you don't outright use upsetting words, but calling that behavior out is criticized.
I don't subscribe to this idea that "civil" is equivalent to "use nice words". To me, "civil" is about how you behave. If you curse but treat other people with respect, that's civil. If you use nothing but benign words arranged in a way that treats other people without respect, that's "not civil".