I just came across, in normal browsing of the site I am a moderator on, another post from a drive-by user which had legitimately been deleted as "spam or rude or abusive".
In a way, that's great, because it means that community flagging and moderation works. No moderator intervention required. Ideally, that should be the end of it.
Unfortunately, my experience is that even just one such post is a pretty good indication that the user is up to no good. Appropriate action to take at that point can range from nothing more than a quick review, all the way up to notifying moderators across the network of the user account in question. But these posts are awfully easy to miss, because by the time a diamond moderator comes around, they may have been pushed off the front page and they may already have been dealt with (so don't show up in the flag summary view either).
Hence a humble request for a new feature: An auto-flag raised on the post whenever a post is deleted as either "spam" or "rude or abusive" purely by community voting/flagging. Since a moderator is already involved if a moderator casts a "spam" or "rude or abusive" flag on the post, there is no need to raise an auto-flag for those cases (if the moderator is for some reason trying to conceal that act from the other moderators, they could just dismiss the autoflag as well, so nothing is gained from the autoflag in that case).
To help reduce the problem with a huge number of flags on high traffic (high spam) sites, this might be selectable by the moderators of each site in communication with the community managers.
This was raised by Monica Cellio in a semi-related answer three years ago, but doesn't seem to have gained much traction (or spurred any discussion) there.