Again, it should be looked at as case by case, if the seller was not in control and didn't do the scam, why tag them? Aside from the fact that people dislike sellers. The account that the scam was done on is what should be tagged.
Imagine someone hacked account of satoshi (if it wasn't blocked) and sold it to someone for signature posting. The buyer will fairly post some low quality things for getting paid and will never scam anyone. And what about a reputation of original owner of satoshi's account? If he's not among us at the moment, has it no value anymore?
If someone pretends to be someone else it is shady by itself. It's not just about that I don't like sellers. If someone will decide to sell his own account, well, I think at least neutral tag is needed, but, well, it's not such a big deal for me (for some others it is a problem). What I don't like is that account trading motivates hackers to hack old accounts. And buyers pretend to get background of the original owner for their own and ruin his reputation.