Nostr's biggest challenge is spam.
Nostr allows clients to generate their own identities (keys) which, while good for portability, makes spamming trivial as there isn't any cost to creating new accounts as there is with traditional email verification.
Unlike Pleroma, Mastodon lacks adequate moderation tools; something I've complained about in the past. (RT: https://noauthority.social/@eriner/111970948469784642)
I don't want to mute the Nostr bridges, but I will if this continues.