I don't know, I often encounter [flagged] or whatever it is that happens to bad comments in the middle of a thread. It leaves me wondering what was actually said.

So it happens already, just for different reasons...

There shouldn't be a need to delete one's comments to achieve a right to be forgotten, only to remove the identifier of the user who made them.

"Giving every HN user power to delete all his comments will make HN unreadable."

No, I think it would be so rare it would not make a difference.

For that 'small intrusion' on your HN experience, you get a hefty dose of privacy and security protection.

I would gladly agree if HN allowed people to 'delete all comments'.