First off, this is a guest-only board. The idea is that a rumor is started, and like a game of telephone, as more people hear it, the rumor twists and changes. But why only guests? We feel it's a kind of cheating for a character to be able to respond directly to the rumor. This is not an in-character board. Just like through a grapevine, you hear things and you deal with them.
So someone starts a particularly nasty rumor about your character. You can acknowledge it, deal with it in a thread. You can ignore it, only acknowledging it to yourself (maybe in a journal). Or there's always a chance that your character doesn't even know about the rumor.
People are more likely to hide behind anonymity and say things that they would not say if you knew who said it. This is called trolling. I'm sure there will be some troll-like rumors started, but don't take it to heart. I, personally, would feel flattered that someone took the time to think so creatively (or whatever) about my character. But it doesn't mean that my character will ever have to deal with that rumor. That's the out for this forum. If the rumor is particularly hurtful, nasty, and downright crude: don't acknowledge it. But, if it's not so bad and plausible...use it for plottage. Think outside the box and be amazed at how much fun it is!