I'm not sure forking the discussion is a good idea, especially to a site that is likely not well indexed by common search engines. It's also not clear to me how linking, questions, and long-term durable / searchable discussions would work.
I understand Slack's desire to more traffic through their site, but in this case I don't think it's a good fit.
(I still miss Usenet, so you'll have to forgive me. Even using a Google Group makes me pine for the good-old-days on decentralized ownership and control...).
Cheers,
Chris