It occurs to me that the ideal forum probably would have these three attributes.
- Each comment can have multiple children. Conversation threads can be followed even after they diverge (e. g., when two people reply to the same comment).
- Each comment can have multiple parents. Conversation threads can be followed even after they converge (e. g., when one person replies to multiple comments).
- All comments are easily searchable by full text and permanently archived. Conversations can be found and read long after their original production.
Compare some real conversation platforms.
- On Reddit and Voat, a comment can't have more than one parent. Conversation threads can't converge and be consolidated. If I want to reply to multiple people with one comment, I have to use username alerts for all but one of them.
- On XenForo and vBulletin forums, a comment can't have any children. You can follow a conversation thread backward, but you can't follow it forward!
- On anonymous imageboards, archival is temporary, incomplete, unsearchable, and/or conducted primarily by third-party sites.
(I don't at all understand the popularity of Discord.)