*Started Emacs 25.0.91 with 'emacs -Q'. Although the list of "Recent messages",
below, does not show it, the Ediff Quit prompt in the Minibuffer is displayed as follows:
Quit this Ediff session? (y or n) switch-frame-
with the " switch-frame-" characters being extraneous, of course. If one
enters something other than 'y' or 'n', the re-prompt also contains the extraneous
characters. So far, this is the only Minibuffer prompt I have encountered with this
problem, though I must admit I have not done a lot of testing.