[gambler]

About a decade ago I've been thinking about how to design a good discussion platform, and the ideas I came up with have a lot of similarities with what you posted. I think that encouraging long-form communication where quickness of replies is not an inherent advantage and where there are costs to posting (as opposed to not posting) would be great for improving communication quality.

I also think that visual design cues matter much more than people think. Simply having large text fields to type in and clean design where large posts are readable really changes the tone of dicussions. I've seen this on many websites.

Another, newer, idea I have is that there should be some cost to finding/reading new content. It's probably not what you imagined right now. Here is an example. Let's say you have a popular YouTube video when someone plays Overwatch. Instead of the garbled toxic mess we have right now, comments could be split into different tabs/topic. There could be one tab where people discuss the strategy of the player, while in another tab people could discuss balance of the game as a whole. The "cost" of reading comments would be reading the titles of all tabs and clicking on one. It's not much, but I am 99% sure it would do miracles for decreasing toxicity.

People behave much better when they feel they are interacting in a social "space" with a defined (if open) group of other people. Information overflow destroys this feeling in an instant, no matter what other social features you add.