The willingness or need to enforce seems to correlate with the measures a company requires you to take on signing.
* TOS - a simple checkbox - or even just a "continue button"
* Moderately large purchase - type your name
* Larger purchase - draw your name
* Major contract - use this widely recognized signature flow
That's really just a defense against deleting the wrong repo. If you're typing in the whole repo name, including the account it's under, you're very likely to know which repo you are deleting when you hit the button. (Consider the horror scenario where you both own an org repo and have a personal fork, and you mean to delete your personal fork but delete the main repo instead.)
The moment you write out the private key it's no longer secure. Anyone who sees it (and has a good enough memory) could copy the key to another contract.
You'd need to perform the DSA algorithm in your head on the content of the contract, using your memorized private key, and write out the resulting signature block.
* TOS - a simple checkbox - or even just a "continue button" * Moderately large purchase - type your name * Larger purchase - draw your name * Major contract - use this widely recognized signature flow