Good questions and definitely worth pondering. But one major correction:
As for the echo chamber, that is entirely up to the user. I intentionally follow and keep an eye out for posts from users who I know often have different ideas than I do. cliffelam, minimum_wage and cgod all come to mind for different reasons based on different topics.hubski's founders have in the past mentioned twitter when attempting to explain what hubski's model and mission is.
We have mentioned Twitter to explain functionality because it's an easy way to familiarize people with the idea of "following people" instead of only having dedicated topical sub-sites. Never though have we used Twitter as a model for our "mission". It may at first seem as though this is a small distinction, but it's not. We have a very specific mission for the site. Our mission is to provide a place for the thoughtful discussion of ideas and information. This isn't a marketing ploy, it's what guides every decision we make. -not splitting hairs here, just want to be very clear that "Twitter" isn't our mission.
I thought about using the word 'mission'. It isn't exactly what I meant. Knowing people's usernames equates more to knowing twitter handles than to knowing reddit handles. I'm not convinced that merely following a handful of people who have outlier opinions on politics or life or music is enough to escape this process I'm thinking about. We'll see.