Allow superusers (non-moderators) to add tags to a post

Most people don't add tags to their post or they don't add very good tags to their post. It's a lot of work for a community manager to add tags manually but it seems like a simple thing the most engaged members could help out with, without needing moderator privileges.

I'd love to see the ability to add tags to someone else's post added as a privilege option for custom user roles so we could grant this access to members who reach a certain status. I'd also want it to work from the community side not the control side so they don't need to have any moderator access in order to do it.