I do not think this is a big problem, not just because it is a common thing to have on forums, but because we had the post count next to the avatar already. Even without the stars, the post count always had more or less the same function and implications.
I understand it can create a sense of elitism and negative incentives (for posting a lot), but these things were already in place with the post count. One thing I always liked (though plenty or reasons not to like it I guess) is a "rep" system. Simply because instead of creating an incentive to post a lot, you create an incentive to post something helpful. Also, if you are going to distinguish member of the forum, I guess you might as well do so based on how helpful they are to the people around them.
That said, to me it is no big deal. Most forums have it, can not say it ever bothered me.