I can ask you something, it is allowed that a user sells bitcointalk account yes or no, and because they reason, because I would like to work on that topic reporting
Is it allowed by forum policy? Yes. You won't get banned for selling/buying forum accounts. Although, that being said you will receive red trust from DefaultTrust and other members for doing it just as you've found out here.
Forum accounts were sold a few years ago and it wasn't too much of a big deal then. People did scam with them sometimes, but others just used the accounts to avoid ranking up issues which I believe theymos stated at some point he wasn't against the idea of this happening.
Although, nowadays it's a much bigger problem. Account sales are almost always used for either scamming, signature campaign abuse, or they have been hacked from the database leak a few years back. So if you are asking whether you can get banned for trading in accounts then the answer is no. But, this doesn't mean you should trade in accounts as it's highly frowned upon by the community and a select few actively look from sold accounts. In fact there's now a password/email change log that I would bet that a few users are downloading and watching out for suspicious activity on accounts.