Academia - Is this sort of blatant trolling common on Academia SE?

does it happen with some regularity?

Yes, I saw it before. Copy and paste the answer from somewhere, leave a comment asking for bounty and then delete the account. Actually, this is how I caught it. The moment I saw it, I knew it's coming again. So, I took the first few lines of the answer and Google it and then found where it came from. I then flagged it.

I am going to provide another example of an incident of this kind. Hopefully, the Mods can tell us whether they are the same user or not.

A deleted answer for the question What to do when a good article is published in a predatory online journal that disappears?

The deleted answer was copied and pasted from https://www.sciencedirect.com/science/article/pii/S0917504017300217 as pointed out by @InquisitiveLurker at that time.

And as you can see the comment (now deleted) left by the poster

@Joe74-Now that I have given an answer to your question,please award me a bounty worth +100 reputation within 5 days from today

To me, if this is not the same user, then the user who trolled this time must be a copy cat (pun intended).

This is the first time I’ve seen such behavior as a moderator. However, we try to stay on top of getting rid of trolls as soon as they crop up. So please flag any such behavior and we’ll take care of it.

According to this question on the main Meta you cannot actually award bounties to deleted answers, even though the +100 button looks active.