Threads feature parity

[rafalp]

This is a checklist of features that Misago's threads currently implement that new pages should also implement. Already implemented or WIP features with progress tracked on their PRs are removed from the list to make it less terrifying to look at.

Editing posts

• See edits count
• See edits history
• Revert post edit

Solutions

• Label post as solution
• Display message about thread having a solution
• Select/change/remove solution

Watching thread

• Watch started thread
• Watch replied thread
• Watch on invite by other user
• Watch or unwatch thread UI

Posting

• Quote post

Richtext

• Break long words

Posts

• Hidden post with visible contents
• Hidden post without visible contents

Notifications

• Notify other users about new replies

Misc

• Get post's permalink
• Metatags
• Page header
• Breadcrumbs

[rafalp]

I've started breaking up this massive list of things to do into sections for bigger clarity.