Guidelines are great and I don't mean to sound rebellious here, but this board works because of the many regulars who have adopted a culture of tolerance and helpful criticism. I would expect that to continue whatever the "rules."
It makes me a little uneasy to put guidelines on what should be offered in terms of critique. Just like we have many levels of experience and talent in photographers, so do we have many levels of experience and talent in offering up critiques. While Photo John can (and does) offer long and insightful critiques, others may be limtied at times to saying: "it rocks!" which can sometimes be a very helpful comment.
By the same token, people will occasionally say something that seems pretty rude to me, but is also very helpful in getting the point across. What's rude? It's hard to define, but it brings me back to the culture thing. As long as we have people like gahspidy, chink, walterrick, liz, oldtimer, liz, and many others critiquing and setting a standard, the bad seed/troll types seem to go away after a while or reform. (Although we kind seem to have one now.Perhaps its too early to tell.)