Why do we need a post count at all?
It would only result in threads like:
"Whooot, 100th post11!!!"
Which is just as rude as when a new update comes out, like "The user ... has won this weeks Weekly Raffle!" and the first comment to it says "First post!" instead of "Congratulations" :/.
If that would be the only aim for it, I think we are better off without it.