I strongly don't like accounts trading but mainly because it encourages accounts hacking. If someone sold his own account... well, it doesn't look good anyway, I'd say it looks shady anyway. But well, if it was years ago and it is the only one shady thing about the account which was active all these years, I don't think such old things should be digged. Especially because there was another consensus about it away back.

As for new cases there's no doubt that new accounts trading should be tagged negatively for both a seller and a buyer. We can consider neutral tag in case when we sure that the true owner is selling his account totally publicly, in exceptional case. But in new cases it should be tagged anyway.

We can say that cases before 2018 or something like that are too old for digging if there's nothing else bad about that account.