Plenty of clients don't support all features of Nostr. Did you know that Damus doesn't support GiftWrapped messages, Communities, and plenty of other NIPs!? Damus doesn't support exporting your NSEC though.
Can you sign into Damus with a nsec from another client?
Yes. They never lock down your account.
Yep. You can. People do it every day!
Damus absolutely does.
Does** typo
Have you told Vitor and Holdbod your highly interesting take on them?
I am going to send you a bunch of GiftWrapped DMs.