I've already had this user banned for plagiarism. His post history is a smörgåsbord of spam, nonsense, burst posting, and plagiarism. Completely inactive all year, but made 40 posts in the last 24 hours as part of the Yobit campaign. I know yahoo is on the case, but with these kind of spammers waking up left, right and center, hopefully it won't be long until this campaign is similarly banned.

Now, I am 100% sure you are right when you figure this user has multiple accounts. If you can track any of them down, you can report them for ban evasion and get them banned too.