Steps to reproduce:
- Setup authcache, configure a role allowed to post comments, allow cached pages for this role
- Create a user with the role created in previous step
- View a node with open comments
- Post a comment. Result: The new comment is visible
- Reload the page without reposting the data: The new comment vanished
I regrettably do not understand how cache-invalidation works in this case. It would be great if the original developer could shed some light on the stuff he implemented in 6.x.