If you change
$countposts=1 to
$countposts=0 then there is
no way on earth that the post count will change for the user when you delete.
it WILL change if you run "update counters", because that operation is a simple COUNT query of the database. So, if you don't want your users' post count to ever change, then change $countpost to equal 0, and never run "update counters"