Or are there some forums that don't have it so the posts in there register? Just curious, I'm a lazy perfectionist, and it I'm at 98, should be like 103 now..
Report Topics don't get deleted. (Do you delete them on your forum? I keep mine around for at least a year. And if there is discussion in the report, I keep them around for longer.)
I think post count goes up also when you report a post and down possibly when the report topic gets deleted.
Posts don't count in this forum, they never have. Your post count doesn't go up when you report a post on stock vBulletin, it might go up here because reporting a post automatically adds a thread to a hidden forum. You are correct about the last part. If a thread gets deleted your post count will go down when update counters is run via the admin cp. Although at this site they simply move deleted threads to a hidden forum so it may or may not affect your post count.