Several times, I thought I have, but the person turned out not to be who I thought they were. I have certainly known people who posted on more than one board I frequented, but I knew what their usernames were on each board, and they were different boards for a similar topic.
This isn’t about someone who uses the same username on all their message boards, which as we all know is generally not a good idea.
I know you said this doesn’t count, but I recognized someone on another board by their posting “voice” before it hit me that they used the same name for both locations. Not that I can judge, since I do as well.
I also realize you said this wasn’t what you were asking, but I actually did find someone on a completely unrelated board with the same distinctive name as someone on here, so I’ll assume they’re the same person.
I don’t think I’d be able to tell just by “voice” if the name wasn’t familiar unless they used very, very similar phrasing consistently or told the same story line (like how some posters made the connection between umkay**** and someone posting on a pregnancy board).
I realized last year that a poster who used to post here (now she posts on one of the other boards like Giraffe’s board, IIRC) was my neighbor from across the street while we were growing up. Pretty cool…
There are at least two people here I knew on another Board but I use a different name here so one doesn’t know me (and doesn’t post very much anyway) and the other has probably long forgotten that I PMed him about something related to the other Board after he had stopped posting there.
I’m pretty sure a couple of people here are, like me, also posting on the io9 boards, and their sub-board The Observation Deck. Sometimes I think I recognise a username there as also being from here, though I’m never sure if it’s just because I’ve been posting there for a few years now and getting confused.
I’m pretty sure that I’ve recognized people on the Order of the Stick forum who also post here from their names and things they’ve said. And I knew the forum names on the defunct City of Heroes forums of several people who post here.
Also, on one sci-fi board I’ve seen a poster talk about the same incidents in their life simultaneously here and there under the same username, so they are obviously the same person. Also on the same board I’m pretty sure a certain creepy banned pro-pedophilia poster showed up using the same name they used here and got banned there as well.