Responsible Lightning services that offer NWC really HAVE to provide some way for a user to get back into their account if they are locked out. We use a 40-year-old technology -- email -- along with a 15-year-old technology -- 2FA.. because we're conservative. A service could also use Telegram, SMS, etc. But fundamentally a service MUST provide a way for a user to recover his/her account. Just "login with your nsec" is not good enough. Users will fuck up, lose their nsec, and lose their funds. That's our opinion. Not everyone will agree.