If someone's allying with a domain that spams my periphery with noise, i really don't care about them and wouldn't bother validating their signal as a user in the first place.
Being able to have a nostr address point to so many free domains, and they choose the spammy one? No thanks, i'd rather block the domain by default. If they want to be seen by me, they're welcome to do the "work" and change out their address.