One of my hopes for Discourse AI integration is that it will allow conversations to occur in a natural, human manner while still allowing a forum to function as a knowledge base for users who have not been following the full conversation. Semantic search (especially when searching within a topic) will help with that. Another approach would be to use AI generated topic summaries to break a topic into subjects.
For topics that have a sufficient number of posts, the summary could outline the OP, then have a “subjects discussed in this topic” section. In a similar way to how clicking the “(n) posts in topic” button on the usercard extracts that user’s posts from the full topic, each subject discussed could have a button that allowed the sub-conversation to be extracted from the full topic.
This might also be useful for moderators who were wanting to separate long topics into multiple topics.
Note that this is less testable on Meta than it used to be. An effort has been made over the past few years to keep topics relevant to the OP.