Provided your nsec is not transmitted by a nostr client and all message signing is client-side, the private key should be safe. The operative word, of course, is should.
Discussion
Accounts get compromised all around the world, all the time. If it's just one of your many accounts, the damage is limited. But if it's your one and only nsec, and you use it all over the place, that's going to suck, a lot.
Agreed. I was simply saying if the nsec is limited to the client such as primal to login when you want to post notes, it should be safe.