Shoutbox

I personally don't like the idea, even if it just triggers a warning...
If a user needs warning about their behaviour a mod will notice, or even a member could just send a friendly PM to a member who is acting inappropriately. When John Anderton's forum attitude was annoying I just sent him a friendly PM with a few tips on how to help people out, where to spam, and generally what to do in situations like the sponsor...He sent a PM back and was polite and told me that he would try to do everything I suggested...doing this on a personal member to member basic is much more effective than having an auto warning to the member, or even a standard warning...
Also I don't think the reputation of a user is linked to their need for banage...they just may be a little arrogant...