Asfaloth12 what's the "Reply to discussions" permission for that restricted tag?
The policy for renaming a discussion checks both the dropdown setting for the time limit AND whether the user is the author AND whether they can reply to the discussion.
The reason it checks for ability to reply is probably a shortcut to easily integrate with extensions like Lock, so that locking a discussion also prevents regular users from renaming it, but not moderators.
A similar system is used for the post edit configuration. I actually created this extension in the past to offer more options for the post edit permissions. Something similar could be done for the rename permission if someone has a use case where users can't reply to their discussions but should be able to still edit the title https://discuss.flarum.org/d/26521-advanced-post-permissions