Is Trade chat too sophisticated for you? Would you like the bothersome achievement spam to instead be endless hilarity? Do you enjoy abusing horse carcasses? If so, AA is the addon for you!
AA will prepend the A-word to all achievement links you receive, both when someone links an achievement and when the game tells you about an achievement you or someone nearby has achieved. That's all it does. It does not filter messages, remove any of their content, or report what the messages say to anyone.
Installation:
Drag the folder from the zip into your _retail_/Interface/AddOns folder. That's it.
Options:
There aren't any! Because I don't see what you'd need to change about this piece of perfection nor can I be bothered to make a UI.
This is a silly thing I made at 1 AM giggling to myself. If you actually know Lua and would like to expand on the idea, feel free.