While this is highly effective, spammers do frequently send gibberish posts (such as ajliabisadf ljibia aeriqoj) to test the spam filter for moderation system detection.
The songwriting process is sort of like automatic writing for us; make up some gibberish to go with a tune and then whittle away at it until meaning emerges.
These gibberish posts will not be labelled as spam (though will cause no real benefit to the spammer) and will still clog up a comments section of a blog.
