Well, I think this is why I really like Webmentions as an expression of intention. In order to send one, you need to have your own blog. And you need to link back to the post. (AND, technically, you need your post laid out with microformats!)
This acts as a kind of wall around the garden. It acts like a gate. If you’ve got the code, you can get in. But likely you’re going to move on. There are just so many other places to harass and cause mischief on the web today. (Contrast with the massive silo gardens—if you are a member, you have all access to everyone there.)
I think a great benefit of social media could be that it provides an outlet for the masses so that careful enclaves can still be formed on the open web. I mean, look, there will always be bad actors in a group—groups seem to have a half-life where they grow too big and destabilize, the birth of a whole new era of drama and rage.
As for discovery, I think every blog needs a list of links to other blogs in their community. It’s like your friend list, but can be so much better than that. I want to read what you’re thinking, but I also want to know where else the discussion is happening.
Webrings are opaque; I can’t see where I’m headed. But a link list (blogroll, whatever) is like a gift.