Originally Posted by
Kanegasi
You don't need an addon for that. When you want to turn off player chat, just right click the General chat tab, select settings, and uncheck everything in the "Chat" and "Global Channels" sections. These settings just prevent these events from showing in your window, you won't leave any channels or guild or anything like that.
If you want to hide everything but NPC chat, including loot and yellow system messages, uncheck everything in "Other" except for "Creature Messages". Make sure all those creature boxes are checked, those are the NPC events.