Something unusual is going on. Lots of posts are being deleted around the forum, but people aren't being notified by PM that their posts are being deleted.
It would be nice to know what posts/threads are being removed.
It's just moderators doing their work to keep this forum a tiny bit less cluttered with garbage. If you post in a thread that later gets deleted, you will not be notified like when your own post or thread gets deleted.
Just keep track of your recent posts, and you'll notice which of your posts has disappeared. If you see your post count decrease in a frequent manner, it should be a proper signal that you need to avoid posting in certain threads.
So no, there is nothing unusual going on here.