Suggestion Against Gil Sellers?
Allow us to have a selective ignore? Basically - give us the ability to ignore certain level ranges from whispering us, communicating with us, and inviting us to groups (but we can vice-versa). Basically, allow the lower levels to whisper if they're added to a friend's list.
With the exceptions of free companies, of course. Needless to say, if your friend is making an alt, he'll tell you.
The ignore would only work if you set it certain levels below you. It can never be at your level or higher.
Could this work?
Suggestion Action against Gil BUYERS
Ban them, ban them hard.
That is all.
OK, obviously they have to be certain that someone did in fact buy gil from a confirmed RMT seller before banning them.
Other than that, and as have been suggested before;
Make blacklist entries account wide. This would slow down RMTs by costing them more accounts in the long run, but it would also have a superb effect on reducing harassment as a player being harassed would be able to block not only the specific character being used to harass them, but the entire account, so the offender cannot fall back on alts to continue the harassment.
Add a "report as RMT spam" option on the right click on a name in the chat log to enable faster reporting of RMT spam. most people I know have given up reporting this crap because it a) takes too long for each report, b) they only ever get a automated form letter reply anyway, and c) they don't want to spend their free time when they should be playing, working on RMT spam reports.
Oh, and for crying out loud please take some action against the players who are actually buying gil from RMT gil sellers, make the action blatantly obvious to the player base so that there is a deterrent effect please.