Do you have a file with that name. Get one with "ECHO foo > %@CHAR".Not reproducible here.
You get that odd prompt anytime you specify a filename consisting entirely of characters >= 256
Quite right!/Q doesn't seem to have anything to do with it; you get the same prompt without it. DEL is acting as if /P had been specified, though it wasn't.
v:\> dir /k /m [EMAIL]%@char[/EMAIL] 3/19/2012 23:06 5 π v:\> del [EMAIL]%@char[/EMAIL] V:\π : Are you sure (Y/N)? N 0 files deleted
After a closer look, it isn't the /P prompt. It's the delete-all-files-in-a-directory prompt, the one that /Q is supposed to suppress. Only (1) the file named isn't a directory, and (2) /Q doesn't suppress it.DEL is acting as if /P had been specified, though it wasn't.