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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
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Permalinks
Permalinks to root posts
No change to existing UX. Permalinks to root posts take users to the channel, scrolled to the highlighted post.
Permalinks to child posts
If a post contains a permalink to a child post, clicking on the permalink would load the linked-to thread in the RHS with the linked post scrolled to and highlighted.
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Marking Channels as unread vs. Marking Threads as unread
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