Another way to put it is, if you want to speak to the whole network for years to come – you just really can’t do that through Slack. Your audience is limited to whoever isn’t overwhelmed with notifications today. If the answers you seek are only helpful if they’re immediate (e.g. “where’s the bathroom?”) then Slack is perfect and you shouldn’t bring that question to Discourse
On the other hand, Discourse posts will come up in Google searches, and things are structured around longer-term knowledge building (e.g. everything under a revisable topic/subject with topical tagging, the top post editable by authors and is convertible into a community wiki, a hierarchical category system you can continuously evolve and reorganize topics under)
While Slack is quick and easy, if your goal is to share knowledge with a wide audience it’s ultimately a lazy and ineffective path vs organizing a readable post under a searchable topic. If you want to maximize for reach, post in Discourse first and then promote a link to your post in Slack to get the best of both worlds
Consider how, right now, we’re building on a conversation started two years instead of just having it again from scratch for the 18th time, and creating a semi-centralized discoverable destination for someone to gather what the network thinks about Discourse