The action itself is trivial, sure, but that and the quora answer itself kind of indicates the issue has been living in their head for at least 15 years, which is a rather long time for a dumb quip to be taking up any amount of mental space. Most people wouldn't even think of the idea of taking a domain name for the purpose of an internet argument. Granted, most people don't have that internet argument continuously referenced for decades, but I doubt 99.99% of later readership outside of the original mailing list were thinking about the name randomly being called out and were more interested in it solely for etymology's sake.
But it's not just a "quip", he mentioned some internal squabbles that discouraged him from contributing, so not a trivial thing to forget. It's also constantly reinforced as a meme, so hard to forget, so again the tiniest of axes works just fume to justify trivial actions like writing a response or getting a domain.