I had no idea what was going on with e/em/eir. I have never seen them used anywhere else and thought there was some kind of inside joke on lesswrong, something like a play on the word atheist as a'th'ist, as in someone who doesn't believe in the letter combination 'th', or maybe a bad HTML parser trying to insert a th tag, because they seem to be used where the/them/their would be used. It was bugging me enough that I searched for [space]eir[space] and your comment was the first result to directly address it.