Actually I don't think this is really possible because PostCount uses internal values that are crucial to the forum working, so you can't mess with them.
The only way to do this would be to write a plugin that adds a new field and handles tracking posts on its own, then use that data instead of the core data.
Answers
Vanilla Forums COO [GitHub, Twitter, About.me]
The only way to do this would be to write a plugin that adds a new field and handles tracking posts on its own, then use that data instead of the core data.
Vanilla Forums COO [GitHub, Twitter, About.me]