Actually, there is a third possibility that exists because of the rules for the new servers.
By playing on Aradune you agree to:
Absolutely No Automated/Unintended Game-play, any incident of automated gameplay is immediate suspension, second offence is a ban including Aradune associated accounts.
Boxing any more than 2 characters will result in the following actions taken against your account. First Offence: A written warning from the GM. Second Offence: A 7 day suspension of account privileges on all Aradune related accounts. Third Offence: Permanent ban on all Aradune associated accounts.
Notice that last part? If you get caught playing more than 2 characters on Aradune and get a third offense warning, you get ALL of your Aradune accounts banned. Note that I'm not saying this is what happened. I am just saying there are a lot more possibilities to get banned on Aradune than ever before. If you do buy an account for Aradune (or any server to be honest), I suggest making sure it is one where you get the email address. Some people create 1 account per email and sell you the email along with the account. Some people create one or two emails per new TLP and make tons of toons to sell from that email. Getting the email helps a lot in both security and safety.
All of that being said, with it being so many months after the original poster bought the account, I don't know that HRP is to blame. If someone bought an account from him that was tied to one of his emails and they later cheated, that could have been the issue and it just got everyone banned.
Finally, Swamsam is correct in that a plvl is safer than a used account, but a used account where you get the email and no CC was used, is also pretty safe.