Forum, yes, a bit. But that’s centralized. I want to own the copy of my own notebook and what’s in it, but still communicate. On a forum someone else (typically) owns it and might take it down.

The other option is to use a forum or aggregation hub to aid in discovery. So we might have our own online digital notebooks but syndicate copies or links to our content to a site like indieweb.xyz where others could subscribe to a topic (similar to Reddit), but there’s still two-way conversation capable between individual users who still own and maintain all their own data without worries about corporations memory-holing it. The best of both worlds? (See https://indieweb.xyz/en/commonplace_books for a potential case in point).

Syndicated copies: