After jam etiquette?

Well I have finished my first LD (thanks for existing LD!) and now I am ready to start voting and feedbacking.

But I wanted to ask the community, is there any unspoken / unwritten etiquette to follow? If I entered as a COMPO, should I only vote and comment on COMPO entries only? Or can I vote/comment on JAMS as well? Is it generally OK to be critical when necessary?

What about incomplete jams? Are these OK to vote and leave feedback for? I feel like anything I would say would be moot because it is incomplete.

Anything else?