Just to make a few things clear from what I can tell from the OP here as well as the modmail case.

From what I can tell the /u/N-A-V account was deleted and then remade.

If you delete an account on Reddit you can retake that username when making a new account.

We have a bot that automatically removes users that make a sales thread that don't meet the karma and/or age requirements.

He was able to intially post when he met those requirements which was when you sent us a modmail. It was odd because you told me he refunded you prior to switching to selling to another user then finally deleteting his account.

When he posted the OP of this thread

He was a new account (Yes, I realize I am too, but he was at -2 karma)

His account showed as new and -2 karma.