That sounds pretty good! I would love a separate field for this though, auto-complete is kind of a great implementation for this, I agree!
What would be really cool (and it's not available yet, as far as I understand): if there was a privilege for tagging posts. I use tagging for purposes like marking a topic as solved or as assigned to a specific component. This should not be allowed for normal users, but only for admins.
At the moment, I just remove all tags set by users (most people don't set a tag anyway) and set them manually. But it would be great if there was a setting for that
@rfc2822 I agree. Open an issue on Github for this feature request.