Some examples:
Have apps targeted to different user groups, so that the content they see there appeals to them.
Have people setup and save application settings in a signed event. That event can be called up, whenever someone logs in with their npub.
If someone wants to comment, highlight, or react anonymously, just generate an nsec on the fly. Require proof of work or a lightning payment, to get relay write-access, for private relays.
Put comments into zap notes, as most write-limited relays don't block those, especially anything over 100 sats.
Put your app or relay on an private server or behind a VPN. Let people use it anonymously.
Etc.
The only time that someone should need to login and sign something, with their own nsec, is if they want to publish a note in their own name, or if they want access to premium services.
