I disagree that they should plagiarize without consequences if they are fast enough to delete reported post which ain't that hard if you are using notification bot.
If whoever reports their posts doesn't want them to be notified, they could just use
Report to moderator instead of posting about it.
Imho, in his case signature ban could be enough
Have you seen
his signature?
I don't know what he wore before, but at the moment he clearly isn't posting for money.