There have been points in PS's cycle of roleplayers coming and going where even I, having been around a while at the time, felt unwelcome in roleplays if I wasn't on a certain character that everyone knew. This was when people were leaving in droves, and guess why - and some of the very same people that complained about "the elitist pricks driving everyone away" were the ones that rejected my alts if they didn't know it was me or asked me to log my better-known character instead if they did know who was at the keyboard.*
We are not at one of those points. Right now, we're low in numbers and we know it. We can't afford to be snobs. I concur with those that say don't break character, but add an OOC "[My character is just like this; it's nothing personal!]".
*Not that I'm opposed to being asked to log a different character, if you want me to get someone on I'll probably do it unless I'm already in an intense RP or have like three clients up already - it's just that, at the time, everyone demanded the same character and I wanted to explore some different personalities. I'm quite grateful for people putting up with my making up for the lost time with my kajillion alts nowadays.