All too often, bunny_ears is used instead of fake_rabbit_ears because the former is a much more intuitive (if more ambiguous) tag for the same concept. A quick look at the first page of bunny_ears reveals at least five entries that I have to edit ( https://e621.net/post/show/1178639/ before I fixed it - not even a mammal!), and at least a few more that are not humanoid but are tagged such ( https://e621.net/post/show/1157472 ).
On top of that, rabbit_humanoid has a sizable implication chain (mammal, humanoid, animal_humanoid, lagomorph, which is a pain to remove.
Suggestion: Remove the alias of bunny_ears -> rabbit_humanoid. Create alias bunny_ears -> bunny_ears_(ambiguous) ... or whatever's the naming scheme for unclear tags. Have that page contain information about the two (three, to cover nonhumanoids with those ears?) cases.
Updated by BlueDingo