Imo advice/constructive criticism given politely is a good thing. I would be welcoming to any pointers or tips someone had for me if they noticed I could be doing something better, but there is definitely a difference between offering tips or giving someone concrete advice on what they can do to improve and not really being helpful and bordering on rude. For example, I was in a low level dungeon earlier with a healer who was just constantly nattering at the tank throughout the instance saying things like "You sure take a lot of damage" and "you really make me word hard at healing... just saying." Now, obviously that's not super terrible or anything, but it's also not helpful. So yeah, I'd say tips welcome, incessant complaints with no solutions not that helpful.