Every now and then I get a rash of "deleted posts" PMs from posts I may have made months or even years ago. I'm not saying they were unnecessary. but they are deleting entire conversations.
For me, it never got to the stage of entire conversations being deleted but it is odd to see some more deleted posts in the Premier League thread today (that were made last season).
Very unlikely. A mod probably isn't going to go out of their way to find more work to do. It's usually just down to whatever reports come in. Sometimes people use bots to report posts and sometimes users just go on reporting sprees. Sometimes I think users do this maliciously IE they don't like a particular person so they go out of their way to report infringing posts etc.
It is safe to assume malicious reporting is definitely happening, even if on s small scale. Keeping that aside, regarding the reports coming in, I think the post from mprep explains about the bot. It is still not an automated system, it notifies him (or maybe other moderators) of the post that might need looking at. In the end, the decision to delete or merge would be carried out manually.