Wow, looks good! Great feature everyone will love to have IMO! :)
Enhancement idea 1: Hmmm I'm playing with it now and what immediately came to my mind, that while typing a tag, it should get "submitted" after pressing space key. I believe, there aren't allowed tags with names that contain space...I have this user experience from DTube, when you press space there, it submits the currently typed value.
Enhancement idea 2: Also, if I start typing and then select one of offered tags, the previously typed text stays there. I'd expect it to get deleted:
And after I select advertisment
My text stayed there....
But hey, awesome job!! :) I'll be using this for sure...Also resteeming :)