The introduction of a bank system, where virtual currency is earned in return for making posts, will become a dynamic that changes the way users interact with the forums. Specifically, there will be a trend of unknown magnitude for a user to increase the volume of their posts while decreasing post length due to the reward incentive of obtaining currency.
It is uncertain whether reduced post length would affect the quality of the posts either positively or negatively. In one sense, reduction in length could make posts more succinct and efficient, or people may post more vigorously out of self-interest for currency with lessened interest in quality.
The only certainty is that there would be an increased incentive to post, which would likely lead to increased forum posting.
I believe that posts alone should not generate significant amounts of currency. It would make much more sense that liked posts should generate currency if the goal was to increase worthwhile content on the site.