In reply to Steeve:
> ...it would be fair to assume that if they don't say not to, then it's fine to do it; so you'd be right to send it back when you did it, and your handle end got shredded.
No. You'd be an idiot. Your car does not come with a warning not to drive it into a brick wall.
Look at the handle. Look at your crampons. Realise that banging the former against the latter might damage the former. Refrain from doing it.
If you want to clear your crampons this way, use axes that don't have soft rubber there, or accept the minor nicks on those that do.