If you whack your boots with your poles (whack the sides of the soles)
to knock snow off the bottom of the boot, my experience is that carbon
poles will rapidly fail, aluminum won't.

Hmmmmmmm....... that sounds pretty unreliable. Was this a while ago
(maybe material improvements have been made)?

I was using the NNN BC step-in bindings, raising each boot enough so
that when I whacked the boot to knock snow out of the toe pin area
before stepping into the binding, the basket would pass under the sole
and the pole itself would hit the side of the sole at a point an inch or
so above the basket.

The fiber poles didn't get "cut" -- they just gradually (but fairly
rapidly) disintegrated into a lot of parallel fibers, with no remaining
function as a tubular pole, for the first three or four inches above the
basket.

The local ski shop just advised me, "Yup ... don't do that".