I think forums are a powerful Community Second Brain.
Where I see a challenge is finding a system/structure that works for a good number of the people who are part of the forum — admins, contributors and lurkers. A second brain on an individual level is super personal and some folks might not resonate with its structure when shared with others. For sure though the structure might be the thing another person didn’t realise they were looking for or could benefit from.
So I reckon it’s up to the forum admins and power contributors to help shape the foundation and structure of the Community Second Brain. And evolve accordingly.
I do like the idea of wiki lists.
Another idea comes to mind:
Timely/Recurring Category Summary Posts
For example, every 3 months post a summary of the posts in the Forum Collective category. The summary post attempts to spot and highlight patterns and key themes. Perhaps this sparks a deeper discussion of earlier posts and reignites the conversation. Repeat for each category. Consider dividing up the effort amongst the community. “Hey, , would you like to summarise the Community Design category from October 2022 to December 2022?”
I think this is the principle challenge of any community “second brain” or collective knowledge development system. The system almost doesn’t matter, it’s the fact that getting people to agree on a common organizational scheme and process is tough. It usually needs to go top-down to some degree, at the least a subset of the community who are willing to work more closely together to define a good approach, and then people willing and able to guide others and at times even enforce (at least through light editing) the approach. Otherwise you end up with a less useful, messy resource.
Discourse as a specific tool has a lot of good functions for doing this though:
Wiki posts, as mentioned
Table of contents (plugin/theme component)
There’s even a knowledgebase plugin, although it’s a big rigid for my taste.