Why do comments have to be seven words? I personally would perfer to compliment a game without having to put in extra words for it..

Comment's such as "cool" or "nice game" are considered weak posts that serve only to earn the comment-er extra AP. To decrease these spam posts Armor Games encourages users to post at least seven words for comments. A comment were a user actually thinks and gives input on a game merits AP.

oh i didnt know that i wish i did earlier that would really help some people

although most people dont know this rule so moderators dont take off that many posts

Indeed, Mods do go through games and delete all comments that they think are not valid.

Well, if you made something, a song, art, a game, anything... What would you rather have:
"Cool."
or
"I think it was a really good [thing], I especially liked [this and that] because [reasons]. Good job."/"It was well done, and I really liked [this and that] for [reasons], but I think you need to work on [specific things], since it distracts from the overall impression. If you [do/change] [parts], it will really improve. or at least remember it till next time!"

You need to remember that the comment section is not there for you (even if you prefer to be all short worded and frank and what not), but for the developer to know what people thought of their game, what was good, what was bad and what to improve on and how. It's feedback, not instant AP.

Also, if you are going to write "Lol, nice game", you make yourself sound like you didn't bother with the game enough to have a proper opinion. "Cool" is a written opinion that gives the impression you just opened the game, looked at the title screen, and went to rate and comment.
So, yes. Comments and posts must be over seven words long, because no one has yet accomplished to write out a proper thought out comment in less.

Also, a good tip: If you read up your comment, and you can ask "why??" to it, it is still crappy. "It was a good game, and I liked it." might not be blatant spam, but it is still no better than "good game". It is just slightly less likely to be deleted.

What would it be like if everyone just said "good" on every single game and "yeah", or "I disagree" on every single forum post? A society does not exist with few words. Same goes for the internet.