Isn't it insane Bodhidharma cut his own eyelids?
Usually, such extreme Zen stories are used to illustrate commitment and urgency to achieve enlightenment.

It's said that he cut his eyelids because at some point he fell asleep during meditation, a major distraction for him.

Huiko, a disciple, is said to have cut his arm to be accepted as a student by Bodhidharma.

There are many other stories, some involving cut a disciple's fingers (master Gutei Isshi), others cutting a cat in half (master Nansen Osho) and so on.

As far as factuality, I don't think these stories are believed by zen monks to have happened (at least, the ones harming another being), but their symbolism remain a strong vehicle to convey strong meanings, specially in the form of Koans.