My tablet PC uses a Wacom pen. That pen on the its end has an "eraser"
tip. What I don't quite get is: why is that eraser not *always* used as
an eraser in OneNote?

If I am in pen (i.e. "ink") mode and I want to correct something I turn
the pen over (as one used to with good'ol pencils that have an eraser at
the end) and quickly erase things. If I am e.g. creating lines, boxes,
circles, etc. (i.e. "defined objects"), however, then eraser end
suddenly behaves exactly like the front tip, i.e. instead of erasing,
say a box, I am creating another one.

I find that most counter-intuitive! IMHO the eraser-tip should ALWAYS
act as eraser, no matter would tool I have selected for the front tip!

Michael