Simple addon that filters chat messages from the Trade and LookingForGroup channels per the following criteria:
Trade: Messages that don't contain WTB, WTS, WTT, LF, or PC will be hidden.
LFG: Messages that don't contain LF, LFG, LFM, LF1M, LF2M (and so on) will be hidden.
No configuration necessary, just install and enjoy an immense reduction of chat's usual bullshit.