...move things from a rediscovered old account to this one?

I rejoined Subeta a few years ago because I couldn't remember the username or password to my old account. Recently I forgot the password for this account and sent an email to myself, only to find that one of my email addresses was connected to my old account. This gave me the name of my old account and the ability to change that password and get back in.

I just wanted to know if it's against the rules to transfer all that stuff from my old account to this one before I delete that account.

I'd say it would be best to file a ticket about this matter! They can give you a definite answer that's better than guesses from other users^^ My guess would be no because you're not allowed to have more than one account.

I'd file a ticket and provide proof as to you're the original owner of the account for one reason primarily: multiple accounts.