When two pieces of backer board meet at an inside corner, do I leave a
little gap, fill it with thinset, then embed a strip of fiberglass tape
like I would a wall seam? Or do I *not* use the tape, and (knowing it will
eventually crack down the center of the joint) use caulk instead of grout
where the tiles meet in the corner? Maybe I'm supposed to tape the corners
*and* use caulk instead of grout?

Thanks,
Bob