In your postbit template, you could put (where the post count is shown),
HTML Code:
<if condition="!is_member_of($post, $disabled_post_count_usergroup)">(post count stuff here)</if>
Replace $disabled_post_count_usergroup with the usergroup ID you want to disable post count for.
--------------- Added [DATE]1235063598[/DATE] at [TIME]1235063598[/TIME] ---------------
As an addendum, this would only "disable" post count in the post display, not anywhere else. My bad.