I mean, to use you for example: I could google "EightBitNate" and your GAF account (though I'm not sure if it's archived with the move/implosion), your Bore account, your *incoherently screeching* account would be on the search results. If I had the means/time/etc. to interface with the board API (if available), I could get results from your post history of state, age, name (if provided), etc. etc. etc. off those.
And some folks tie their username directly into their Facebook/Twitter custom URI/URLs. Thereby tying a username to a real name and age/address.
"Doxxing" has gotten very simple because most people don't practice basic privacy. Why do you think my NeoGAF name and Bore name here are different? 1) Because I didn't want bans on GAF being tied to this account and 2) because I know splinter forums that are FAR FAR FAR FAR FAR worse than the Bore (no offense) would be trying to gather any information on accounts.
Great, now the RE mods know I post here :-/
And lol this is priceless:
Dude there's a bot that literally tracks and catalogues posts from people here that jackass weirdos don't like
Assuming it’s the ban catalog thing:
1. It’s just a bot
2. It has nothing to do with doxxing people
3. It’s got nothing to do with finding posts jackasses don’t like
The ban bot has a VIP section that catalogs the posts of specific RE members and it's hosted by Kiwifarms. Do you really think it's outside the realm of possibility that a weirdo from there would use that to keep tabs on someone, put together info to figure out who they are, etc.?
Oh that’s news to me. But how is that different than forums that give you the option to view all of a user’s posts? I know RE let’s you disable it but I’m struggling to see how you could use that to dox someone.
Say someone is careless and isn't thinking about how they could be being watched by people on another site. They might mention their job or their age or the city they live in. They might post a picture of themself that can be reverse image searched. The VIP list obviously makes it easier for that data to be compiled.
You could say "well shouldn't they know not to post that stuff on the internet?" Well, yes, but it happens all the time because most people aren't public figures expecting that their posts on some random message board are being cataloged by weirdos. It's no different than how people don't like being filmed in public even though they're in public.

Also there's a book
About this very thing, Nate. While it's focused on women's privacy-- and a lot of it was "no shit, Sherlock" for me, since I deal/dealt with this sort of shit in the past -- it's practical for both sexes. If you want, I can send you my Humble Bundle copy to read.