I've been playing Infinifactory a block based puzzle game made by Zachtronics where you are given simple tools (conveyor belts, welders, etc.) and have to use them together to construct a factory to build a product from inputs. It's hands down the best puzzle game I've played since SpaceChem (also made by the same team.) The thing I like most about it is when you solve a puzzle it feels like you're building a solution rather than just figuring out the one predetermined route the game designer wanted you to follow. (In fact they have stated that most puzzles are made by creating interesting looking outputs and then making sure it's possible.)

I think you've hit on a key issue that community size plays a large factor in the quality of discussion. Many of the niche subreddits I visit still have thoughtful dialog. I think any community will suffer an Eternal September effect as they grow more popular. One of the ways reddit avoided this was by allowing new communities to form to mitigate this (see /r/gaming -> /r/games -> /r/VideoGameAnalysis) but I'm not sure if there's any way to completely avoid this fate. Another way some communities have handled this is through strict moderation/curation (e.g. metafilter's cost for signing up, strict moderation of /r/askscience )

I think Hubski's method of following users and being self moderating is an interesting idea, especially combined with the focus on slower, long form material rather than "fast food" content. Though I'm sure there will be some people who will complain that the recent influx of users from reddit (of which I am one) has degraded the quality of content. But hopefully that will not be the case.