We’ve been using Slack at Automattic for about two years now. One of the biggest challenges I had with it (and any other chat system really) is losing my place. I will frequently read activity in a room, quickly determine it is not immediately relevant, and tell myself to not forget to come back to it later. In reality I never remember and the idea is lost to the ether of my ADHD brain.
Slack has a feature to handle this issue – you can mark a room unread at any position in history!
Hover over any message, click the ellipsis (…), and click Mark unread.