Not sure if this feature is controversial or not, I've added a "Last seen" label:

I'd rather not have this information, but it's already out there, I just made it visible.

Everything you do on nostr is public, even if you store something encrypted it is still linked to your npub. Clients can prevent this with separate keys that are not linked to your npub but I'm not sure if all clients do this today.

Hopefully this at least raises some awareness about leaked activity on nostr.