It definitely takes some getting used to (if you want to get used to it, I mean, if it's something you're interested in). I am super comfortable commenting on everyone's posts everywhere, now, but that took literally 10+ years of being in fandom spaces. And I am still NOT comfortable commenting to anyone other than the OP, especially if it's off-topic to the original post. That said, it's part of DW culture to have a kind of "open salon" situation in the comments, so people are generally used to that here.

For me, I've turned off the comment emails and just check my DW inbox regularly, then mass-delete comments if I have a post blow up and feel I can't adequately respond to everyone (or if there's a lot of inter-comment communication that I don't NEED to respond to). Then I can go back manually to those posts later, and read the threads if I want to, when I feel more energetic about it.

Or maybe what I need to do is just direct all posts (and comments on public posts) to a wider group of potential participants than I'm used to?

Hmmmm. I don't think you HAVE to, but if your posts/comments are public, then there's always the possibility of reaching more people than you expect. It was the same on Tumblr, right?