We have identified the main issues with Nostr direct messages (DM), listed roughly from most to least significant: 1. Different clients implement different DM NIPs (NIP-4 vs NIP-17), causing a lack of interoperability. 2. Users connect to different relays with little or no overlap, so recipients may never receive messages. 3. Message notifications are unreliable. 4. Spam — the system is vulnerable to unwanted messages. 5. Metadata privacy concerns: with NIP-4, others can see who is messaging whom; with NIP-17, others can see who is receiving DMs. 6. No forward or backward secrecy: if a private key is compromised, both past and future messages can be decrypted. Note: “Nostr DM” here refers to the direct‑messaging feature of Nostr Microblog, not a standalone chat application. They embody different design trade‑offs. This is why we ranked metadata privacy concerns and the lack of forward/backward secrecy lower in the issue list. When you need to contact a Nostr microblog user, consider whether using Nostr DM is sufficient or whether you should use a dedicated chat app.

The relationship between NIP-4 and NIP-17 is similar to: iPhone ↔ iPhone: It uses iMessage first (Apple’s service). Blue bubbles. iPhone ↔ Android: It uses SMS/MMS (the carrier’s traditional texting standard). This isn’t an “Android-only protocol,” it’s the old common language that all phones can speak. Green bubbles. If at least one person in the chat is using a client that supports both NIP-4 and NIP-17, interoperability is no longer an issue.