I can make a pretty long list on why it's a bad thing for users on the forums to have a post counter. So lets skip right to the point:
Is there any good to having a post counter for users on the forums?
I'll start with the only reason I can think of, which is false more often than not. The post counter makes it obvious, to a new member, of other members who have been around and posting on the forums for a while ("experienced").
Like I said, this proves false more often than not. Those who have been around on these or other forums know what I speak of. People who have high post counts but aren't by any means wiser than half the people on here. IE: Trolls who would rather have another laugh today at somoene else's expence. People who played and were familiar with the game four years ago but still post on the forums every day. People who prefer to post in quantity rather than quality. As I said in my first sentence, the cons greatly outnumber the pros... if there are any pros at all to this question.
In closing for my wish of removing the post counters on the forums, if nothing else, it will encourage members to value greater the quality one posts with, rather than the quantity.