I find it even more annoying when people are like "Oh, well, I want to play this character so I'm selfcasting, but I'll hold auditions to see if I can find someone who's better.."
That just shows that people have no self confidence in their abilities in my opinion. So what if you're not exactly right for the character? It's a matter of experimenting with you voice and not to mention it give you some practice. If people think you suck as that certain character, then you'll most likely get a critique saying so with a list of things you could improve on. It's like a learning experience.
And what if you don't find someone you like to replace you? Then not only does that make you seem like you're better than the auditionees, but it's also wasting their time.
So like I said, if you're taking the time to mix, you have EVERY RIGHT to cast yourself as whoever you want. Main or extra.
No producer that opens auditions here is a professional so EXTREME PROFESSIONAL MEASURES do not have to be taken into accord. If you want to selfcast DO IT. If you don't, then that's your choice AS THE PRODUCER, you know?
But complaints like this are part of the reason why I just scout people for clips lately :/
Online voice acting is such srs bizniz.