I just found a connection to 3 more accounts so I suggest everyone look deeper into this too. There are most likely more accounts connected.
If you are going to use posts from a long time ago as evidence of a connection, then you need to account for the possibility that an account has been sold since a post was made. In order to rule out this possibility, you should get the archives of the security log to check for password changes, and use good judgment to consider if an account was sold or not.
I'll just post the connection that I find and if the account is sold it's not really my fight to fight. It's the person who bought the account.
It would help if you let us know if you sold any of these accounts in the past.