Here's hoping the Dev's catch wind of this since they don't have a forum of their own but they really need to create a filter for the in game chat. It's just about useless. Can use it for communication because it scrolls so fast with all the WTB WTS messages from people who apparently refuse to use the Trade channel.
I think a better idea would just be to have a flood filter, and if a player is flooding simply chat-block them for a few days. If players do not use the Trade channel, have them chat-blocked for a few hours. People will learn quickly.