Quoted from Crile1:
1) Don't come in and drop negative comments on a pin in an owner's thread. That thread is for people who paid their hard earned money for that game, or those who are looking for information on that game, or fellow owners discussing fixes, mods, rules, etc.
2) Don't make personal attacks. Yeah, it's in the Pinside moderation rules, but people do it anyway
3) Don't criticize a game in a For Sale thread. It's just not polite. It's like picketing in front of a store.
I pretty much agree with this.
Quoted from greenhornet:
Cool...but this site isn't the government hindering your right to express your opinion. There are literally millions of example of things you can't say in a particular venue that have no relation to "free speech".