Slack is currently not indexed on search engines such as Google, and it's more straightforward to ask a question than search for its answer in the Slack search bar apparently. This leads to duplicate or beginner level questions that can deter people that would be interested in topics that are more in depth.
So I was thinking that incentives and/or rules to search, and ask on StackOverflow if no answer found, then post in Slack, would improve the knowledge accessible from search engines, and would make more space for interesting topics in channels such as #general or #coroutines.
One exception might be issues/questions involving stuff only found in EAP/milestone/beta/alpha releases of Kotlin or kotlinx libs, where issues found might be outdated quite quickly, and where using just Slack could be okay.