Nebulous - I like this post. This is a nice fucking post.
Agree - Self explanatory. I agree with you.
Disagree - I disagree with you.
Funny - You serious?/Actually funny (Generally used when someone's being pathetic)
Bad Idea - When someone says/suggests something that you wouldn't agree with.
Zing - Giving someone an ice pack for their burn.
Informative - Used when someone gives too much or too little information.
Friendly - When someone's really friendly, or outright flaming.
Useful - When someone provides really useful or absolutely useless information
Optimistic - Gay pride, used when someone is suggesting something that'd doubtfully happen.
Creative - When someone posts something so far out there that you're just surprised they did it. Or they post "Meh" art.
Late - Really self explanatory.
Bad spelling - Used when someone has bad spelling
and when someone corrects bad spelling.
Dumb - Imo, this is useless. Used just as flamebait, does nothing to convey your opinion beyond "I don't like you." Just use disagree.
Bonus round
Hot - Stingy bastards giving you useless nebulae.
Quill - Basically
@Blackquill's way of saying "You did good, son."
Good Idea - Self Explanatory
Dumb Truck - Ditto for dumb.