That might not be such a good idea, either. While it's better than removing the function altogether (which, I'm sorry, is a terrible idea), let's look at the extreme sides. Sure, RMT messages would largely be cut down...but what about players who are new, don't have a subscription yet, and want to add people? I know I've done shouts or given raises to people and then teleported away, and then that person would either click on my name in the chat box or search me out later. I would also do the same. If that person went into a duty, I'd just have to write their name down and search them out later since my chat log only goes back so far.
I really think the best thing to do is to either set yourself to "busy" or add another tab just for tells, and silence that tab. That's what I did. I check it every now and again to see if legitimate players have sent me anything, which isn't a hassle to me. And it means I don't see any RMT messages in my chatbox or hear the sound for them at all.