• A way to discuss ideas for the site, vote on them, and incentivize the generation of good ideas. I sense that having this would be huge. a) I sense that there are a lot of good ideas out there in people's heads but that they haven't shared. b) I sense that by discussing things, there could be a lot of refinement of current ideas, and a lot of generation of new ideas.
• More generally, my impression is that it'd be a good idea to subdivide sections for posts. Right now it's pretty much Main, Discussion or Open Thread. Ex. someone who has an idea to improve LW might not think it's "Discussion worthy" (or even "Open Thread worthy"), but I sense that if there were a section explicitly for "LW Ideas", they'd be a lot less reluctant to post. More generally, it'd justify more "bite sized posts" rather than requiring a full write-up.
  • One example of a subsection that I think would be cool is a Personal Advice section. The ability to post anonymously seems like it'd be a useful feature here. Other ideas for subsections: AMA!, Brainstorming/Unrefined Thoughts, I Don't Understand X, Contrarian Thoughts.
• Social coordination:
  • Apartments/living together.
  • "What are you currently learning? What do you want to learn?". so8res recommends pairing up, and I agree.
  • Geographical map of users to facilitate friendships and/or dating. (This already exists. But it seems that a low proportion of LW users added a pin on the map. My impression is that because of network effects, the usefulness of this is very much a function of how many users there are. Also, I sense that there'd need to be some sort of a different UI that with some sort of organization.)
  • Online chat. Like Facebook. I think it'd be a) cool and b) sometimes useful.
• Project ideas. There are a lot of smart, skilled and ambitious people here who want to do good things. If LW made it easier to coordinate and work with people, I could see it having a huge impact.

Harder

• Crowdsource the refinement of posts. 
  • Maybe have an answer wiki for each article that summarizes the main points.
  • Maybe let the author award karma to people who submit a diagram of something explained in the article (I'm a big fan of explaining things visually). Along similar lines, maybe do the same thing for people who submit relevant YouTube videos. Ex. I think that this would be a relevant clip to add to an article about expected value (beware: cringeworthy). (Again, I'm really not a big fan of writing as a medium)
  • Maybe allow collaboration on drafts. And allow the author to award karma to collaborators.
• Side comments. I really think that for a lot of scenarios, this is a much better UI. But I also think there are use cases for the traditional comments at the bottom of the page, and so there should be both.
• Make use of some sort of debate tool. I think there are a lot of improvements that could be made to the current approach of having nested comments. It might be sufficient for the level of conversation elsewhere on the internet, but not here.
  • I should emphasize that this seems like it'd be a large and difficult undertaking.
  • But I should also emphasize how important I think it is. Media For Thinking The Unthinkable largely expresses my views here. I think that the mediums we use to write, think and communicate play a large and very underrated role in determining how well we could think. As a society, we don't seem to really recognize this, and we don't seem to have made much progress as far as inventing such tools goes. The importance of such tools goes way beyond LessWrong, but I guess I'm just noting here that LW would benefit greatly from it. I don't think that there are many legitimately deep conversations on LW, and I think that the limitations of nested comments are a big part of the reason why.
  • Along similar lines, I think it's pretty important for there to be a way to highlight and take notes on articles (currently, most people don't). I've been using scrible. Come to think of it, scrible actually isn't that bad of a solution, but I think it'd be awesome if there were a better way to do this built in to the site. (This is another thing I'd like to see across the internet, but I digress...)