Let me think for a minute... Ok...
On some of the other forums that I visit regulary the posts done in the "off topic" secions (or general chit chat like here) are not countable - that is they are not added to your total number of posts on the board. This for avoiding people getting higher profiles since it is "easier" to post something in the off topic than in the down to earth sections.
Second of all, if people just post to get a higher rank - why exactly do they do it? It is just a rank - you don't become moderator or receive Paris Hilton as special cargo over night (Okay say what you want to say... 8) ) - if someone believe that.
If the rank system is to change - I'd say making some sections "non profitable" or multiply the rank points by 10.
Just my opinion.
Per Qualitatem Optimum Robur