Unreads, badges and notifications
When collapsed threads is enabled, notifications behave differently - see matrix of scenarios and associated outputs here (full spreadsheet of the chart below)
Channel vs. Threads badges
In summary of the above chart:
When a root post with an @mention is posted in a channel, the mention badge is displayed on the channel, not the Global Threads sidebar item
When a reply post with an @mention is posted, the mention badge is displayed on the Global Threads menu item in the sidebar.
Channels vs. Threads unread state
When a reply is posted on a root post that has a mention, the mention badge stays on the channel that has the root post, BUT the Threads view now displays as bolded with a new unread message in a thread you follow
Other Implications to existing features (webapp)
Search
Parent posts behave as-is. The ‘Jump’ action in the hover menu opens the parent post in the channel context
Child posts display similarly, but the ‘Jump’ action in the hover menu opens the thread in the RHS scrolled to the child post
Pinned and Flagged posts RHS
Parent posts behave as-is. The ‘Jump’ action in the hover menu opens the parent post in the channel context
Child posts display similarly, but the ‘Jump’ action in the hover menu opens the thread in the RHS scrolled to the child post
Compact Mode
Displays as-is, but shows the new Thread Footer below the post content
Other Implications to existing features (mobile app)
Search
Tapping on a search result goes to the Single Thread View (rather than opening it up in a modal) with the clicked message in view
Pinned and Flagged Views
Tapping on an item goes to the Single Thread View with the tapped message in view