After I posted my last comment, I tried everything, but like you, I could not delete it except by using the Impersonate function.
I have not read all of the documentation, but it is odd that there is no functionality to delete in the admin area in the first place.
At any rate, I use this “weird” Impersonate function to manage my comments (it’s inconvenient).
As you now know from another thread, the ability to “permanently” delete comments is currently under discussion; the commenting feature in Ghost may not be perfect yet.
I apologize for not being able to provide you with useful information.