In the off case where you are trying to portray missing text, then you can use whatever convention you wish: . . . . . , [text missing], or whatever.
There is no way in heck you can accommodate for every reader/device/font/user spacing/etc. so don't even try. Use the grammatically correct symbol and
IF the
user doesn't like the way it looks, they can complain to the reader/device manufacturer. Chances are they won't even notice...heck, they don't even notice - or care - when there is really bad grammar. They are certainly not going to be as picky as you, the epub designer, are about how thin it may appear.
