In my oh-so-humble opinion, I think that the post count should indicate a poster's experience on the site itself, or be abolished. I understand that the argument is that a higher post count is supposed to imply higher credibility when dealing with ES topics...
I understand that Duru is basically THE ULTIMATE helper on the forums, and he entirely deserves his dizzying amount of coins, because I know a huge part of it was spent helping people.
But, there are plenty of posters, myself included, whose decent post count (most peoples being more decent than mine) includes little more than 'my favourite sword in Skyrim is Chillrend' or 'my character's name is Aromir, he was born in...'

Assuming that last one wasn't in an RP, of course.
But, in any case, there are also those people whose three stars came in a large degree from the *drumroll* trivia threads. A much larger volume than the (counts) one person, the saint Duruza, who attained his coins though being a... Well, saint. (Three blessings, Duru.)
I know I have babbled inanely a bit, and implied that post counts that are mostly formed in trivia threads aren't legitimate, but, oddly enough, that's not what I mean. I mean that using the assumption that more TES posts = authority on the subject is usually simply wrong. On the other hand, coin count based on ALL POSTS may play a role in making the forum an easier to comprehend place for both regular users and newbies. Make all posts count. General, RP, whatever. They imply familiarity with the site, with the community in a real form, whereas the solely TES ones imply... Skill at TES trivia.
Or, in an eventuality I would be equally overjoyed with, get rid of the bloody coins, because as of right now their intended usage is being circumvented by all but Saint Duru.