I don't think there is enough evidence to make the claim that a 4th server would hurt the population of any of the current servers. There is consistently 9-10k on both PvP servers and usually Elysium has another 5-8k waiting in queue. I think the population drops people are noticing are more due to the authentication and login issues than anything else.
You could always just cap the next server at around the same amount as the PvE server if people are really worried that it will draw to many people away from other servers.
They have their twitter feed on the main page, but yeah, it would be nice if they were a little more consistent with updates when these issues happened.
I don't think you would get banned. Innocent people overpay for фекал items on the AH all the time. Not to mention people put items up for way more than they are worth to try and screw with peoples auction data and get them to overpay.