I'm different usernames on different forums, a deliberate ploy because I was once internet-stalked, but I'm pretty much the same personality underneath all of them.
As a would-be writer I have three pseudonyms because I write three very different types of material, so I suppose in that sense, each pseudonym has a different personality.
Multiple personalities society? I don't think so. I've had several ID's since I joined AB but just my one personality. I can be nice to those who are nice to me but I fight back if anyone here is nasty to me no matter what ID's I've had:-)