Since you summoned me, sure. The Internet Detective Way: You've mentioned mixing at clubs in Seattle around that time. Wanna bet you never mentioned mixing at one of them on one of the relevant newsgroups? The Propellerhead Way: You know how people recognize your alt accounts because your writing is distinctive? It's pretty easy to write programs to do that too. One way, not the best, is to use the same algorithm Bayesian spam filters do. Back when I still cared about reddit I wrote a script to match users to accounts on a handful of forums reddit trolls tend to come from along those lines. I'm not proud, but it worked fairly well for users who weren't too terse.
Amusingly enough, the Internet Detective Way doesn't easily go back before 2000. Also, using known aliases search actually pops up my real name for two innocuous messages I wrote in 2001 that I'd completely forgotten about. So that's useful. The propellerhead way impresses the hell out of me, by the way.