Discussion guidelines

I think we should create some sort of a discussion guidelines document and encourage people to follow it.

Possible suggestions to the reader would be:

Don't be verbose:
Use as less words as possible to make your point.
Don't repeat yourself.
Don't repeat others, there's a like feature for that.
If you want to add something just add it without repeating what others said just because you got the same opinion.

Proposals should be suggestions on how to do things. No questions, no general "I want this solved!"-esque things. Use discussions for that
In your votings on don't repeat what others have stated in their votings (block is an exception here). If you want to add something more useful than yes or no, summarize what has not yet been summarized in a voting. Don't vote if you're not fairly sure that you'll keep this opinion. Don't hesitate to change it if you got convinced, but again avoid repetition.

Just my first thoughts, I'm sure more comes up.

This should go as a netiquette, not a participation requirement.

My main aim for the moment is to reduce noise and improve efficiency by reducing the TL;DRs (which I already have some of here, to be honest).

+1 (trying to be short here ;))

Another point:

Stay on topic, if you find yourself making a lot of paragraphs maybe rethink if you're still in the right discussion or rather should split your comment up and create a new discussion and reference the other discussion there as related. This makes it easier to follow a discussion and also allows other to ignore that new topic if they don't feel to be able to participate in it.

I completely agree. I think that staying on topic is absolutely crucial to harbor good discussion.

All good suggestions. :)