That the reason why I think deleting all the threads is useless.... just do a clean sweep and remove all the "spam" and non related plus and messenger posts, keep the posts/threads which are used for reffering. The people put a lot of time in it to give big, detailed answers!!!
Just deleting everything is kind off... errr... lazy of the admins/mods/whatever.... sorry to say this, but if you want to clean the forum then clean it... don't delete it....
Another way of putting it: a huge knowledge base is revised, not erased....
The major problem is indeed: people can't find the answer directly so they ask the same question again and again.... Maybe time to make a good help-file for plus!? Or to make the search option more standing out and user friendly....
About the post counts... Well, in general, they are a good indicator, abuse is everywhere, yet it will be a pitty if all that is also erased. But then again, that's the least thing... it's only an indicator...
my 2 euro's