The incident homepage is the primary way to keep internal stakeholders updated on the progress of an incident. It acts as an "at a glance" view, and a jumping off point later for things like actions and postmortems, too.
Although this isn't the primary interface with which we expect folks to interact with actions, you can do everything you'd do in Slack through the web UI too. Stakeholders can see which actions are being worked and by who, and add new ones, if appropriate.
Active Participants and Observers
One of the things we've sometimes found tricky to communicate is who is playing a specific role, who's in the channel to help, and who's in the channel to listen in. We've split them out in the incident homepage into "Key Contacts", "Active Participants" and "Observers".
Right now the bar to becoming an active participant is quite low (have they sent some messages, maybe helped out with an action or two), but it's likely something we'll improve and fine-tune over time.