I turned off the grid for now as a workaround for the formatting problems. Going back to the original problem, I'm still having problems with that: I mark a bunch of agenda items (scheduled for today) and then do a B s. It reschedules them for tomorrow, no questions asked. If I repeat the process on the same four items, it reschedules them for the day after, again no questions asked.
Not sure if I'm doing/setting something to cause this bahaviour, but it's certainly not what I expected: I thought I'd get the usual date dialog that would allow me to set the rescheduled date. Thanks, Nick