I think you can set a neutral feedback on their profile warning others members of the forum about the not-ownership of those accounts.
Good solution.
This thread inspired me to do a search on members with "pharmacist" in their userid's, and there are some interesting new ones.
The_pharmacist seems suspicious, although obviously I don't own any claim on the word
pharmacist the way JetCash does with his JetCash domains.
One other interesting one is
PharmacistHijacker who registered in 2014 before I was a member. I wonder what that name is all about. Sorry to get so off topic, but this is kind of interesting to me.