People likely would use it. It's a HN account, not a bank account.

Yes, but they shouldn't.

Even though I have no ill intent and it's just an account on a silly web forum, they shouldn't and it would make me sad if they did.

Some of those are apps. Apps should be fine to use those accounts, as they should not contact anything else than HN and HN's API.

But I guess the only way to be sure is to write one yourself.