Which ones are similar to your own?
There are a couple out there which make me do a doubletake while visually scanning a page of threads:
easy_e’s (I think I’ve got that right) and there’s a new doper (or maybe a quiet one) out there with “clay” in his or her name.
It’s kinda funny… I’ll come back from vacation and after a quick 30 second scan of a page of thread titles I’ll think I posted in the last day or so…
quasimodem is sometimes mistaken for me, and vice-versa.
I thought I saw the word “dream” in someone’s name once, but I can’t remember. Otherwise I think I’m the only one who’s dreamin’ 
There’s a Big Kahuna somewhere because I originally wanted that but it was Already in Use
There are lots of other Bigs, Biggirl is one that comes into mind
Easy one here. One of the classiest and most literate people on this board is TVeblen. When I first became a member, she and I would end up on a number of the same threads often on the same sides of arguments. I just know some people thought I was her thinly disguised sock puppet. Then they read my posts and I’m sure they realized that Veb couldn’t write that badly even as a sock puppet.
TV
Mnementh
It’s more an issure (although rarely, since I almost never go) in chat than it is on the boards (unless we’re lazy and only type mnem in a vanity search 
demise for me.
There’s a few variations on robin or robyn about.
There is no General Question here.
I’ll move this to MPSIMS for you.
DrMatrix - General Questions Moderator
I thought DoctorJ was going to come in and do that. Or maybe Doctor Paprika…
At a dopefest recently, when I introduced myself as porcupine, the person thought I was Fretful Porpentine.
And Spiny Norman is of course a hedgehog, so there may be some confusion there as well. 
There’s GreatKat, but the one that throws me most often is Kal…
My sort-of-doppelgänger Mojo is a closer match than your examples. I have even been advised to change my name here just because somebody else calls himself Mojo. Hey, I have used this name since 1980. I have every right to it. Just call me Jomo (as in Kenyatta).
I’ve got loads. Well, relatively…
hayduke_lives!
the_duke_69
dukie
gduke
I think there were more, but I can’t remember them off the top of my head.
I think there’s a PrincessSerendipity around here. When I first saw the name, I thought maybe I had been promoted.
And he considers it a compliment, if you don’t mind him saying so, sir!
Q
There’s a galen out there - recently he’s been posting more often. Personally, I like to respond to his threads to see if anyone gets confused. I haven’t seen him post anything that would make confusion uncomfortable for me - I’m not entirely sure he’d say the same…
There’s some guy who goes by UncleBeer. Doesn’t hang around much.
i was surprised when i saw Acco40 here, so much so that i emailed him to ask how he came up with that username.
Nothing similar to mine, but after viewing a couple of threads, I hereby nominate:
hillbilly queen
hillbillyboy