If you delete a tag from a project, the admin interface reloads, and the info message "Issue untagged with: (tagname)". I guess technically this is a thing that happened (some issues did just get untagged...), but it's not really what you just did.
Metadata Update from @pingou: - Issue assigned to pingou - Issue tagged with: bug, easyfix
Commit b4c3aef8 fixes this issue