When someone randomly comments on one of your facebook posts, making everyone else not want to.
Usually a relative or a lesser-liked friend of yours, or someone that you don't like that is a friend of yours on facebook.
John Doe is gonna go 2 da baseball game!!
Grandma Doe - Hey sweety!! How are you? Say hi to your mother for me!

John (mentally): Oh god, Grandma just performed comment murder!
by lochei May 15, 2010
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One who comments on a facebook status with a random word, or stupid joke that no one understands or everyone hates, therefore causing other people the sudden urge not to comment on it. Usually this person is not liked by anyone on facebook, and in most cases real life.

Also see comment murder
Person 1 (Joe just posted "asdfhsadf" on my status.)

Person 2 (Wow he's such a friggen comment murderer)
by ChAoS x DaRk March 24, 2011
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