Those are old school bots you're seeing, then. Usually used by people who are more desperate to avoid the clickfest than habitual resellers and plot snipers. Current bot software has different tells and the user of it does not stick around after a sale, usually teleporting out automatically to a random location or simply logging out once the bot realizes the plot has sold. The author off the bot has gone to great lengths to make it appear as natural as possible to avoid detection. But if you know what to look for, you can tell who's actually at their keys and who's set up a bot to run for them while they sleep or something.

Jojoya is right though, you should report them to the STF. I can say from experience their response to reports of this nature has been non-existent, but maybe they'll prove me wrong this time.