I've tried both of this sites.

https://discusslr.com/discussions/29

https://sublevel.net/tux/

Discusslr is more like chat and allows you to register without captcha and to reply you don't need to register. SubLevel you need to enter captcha and be registered to comment, it also looks more like Twitter. But SubLevel provides more features like RSS feed of your recent posts.

I've never seen sublevel before. Looks interesting though.