I think the following changes would fix most of the gold seller issues.

1. Log all chat for later review by devs (at least the last 24 hours worth). I wouldn't be surprised if they do this now.

2. Limit character deletion. maybe a 24 hour delay before the character is gone, Eve does this. It restricts the gold seller create random char, spam a lot, delete cycle.

3. Once a day, run a server check for all blacklisted characters. If a character has too high a blacklist count, check the logs from #1 for that character. If they sent RMT messages, lock the whole account, contact owner via email to check for hijacked account, delete account if not hijacked.

4. Log all trades and market actions (already there since there is a market log). Scan once a day for large money transfers, either single items > 1M gil or item stacks > 1Mgil/stack. Filter for low value items only (i.e. copper ore, etc) If event looks invalid, lock both accounts involved. After eval and/or a delay for owner contact, delete BOTH accounts.

Since this isn't a F2P game, each account costs money up front to buy and losing the account would hit the gold sellers hardest. A strong zero-tolerance policy would put an end to this.