The current version of Keychat uses a seed phrase instead of nsec. This has caused a lot of controversy, with many people believing that Keychat does not understand the spirit of Nostr: having a single Nostr ID that is universally used across all Nostr apps.
In fact, the first version of Keychat used nsec. Later, we intentionally switched to seed phrases. Why?
Just like when we use Bitcoin wallets, we now more often use seed phrases rather than private keys. Using a seed phrase is an improvement in user experience. Moreover, NIP-6 defines the basic key derivation from mnemonic seed phrases. A single seed phrase can derive countless Nostr IDs.
Using a single Nostr ID across various Nostr apps focused on public notes is reasonable because users are sending public messages, and they can better accumulate reputation.
However, for Nostr apps focused on private notes, users should use multiple IDs to achieve better privacy. For example, you could use ID1 for close friends and ID2 for work colleagues. Current chat applications provided by internet giants do not encourage users to use multiple IDs simultaneously because multiple IDs affect data mining, reducing the accuracy of user profiling and, consequently, advertising revenue. In this context, using only one ID is a bug, not a feature.
If you use your Damus ID to chat with others on a Nostr app that focuses on private messaging, do you want all those people to see the public notes you have posted?
A seed phrase that is universally applicable to all Nostr apps allows users to choose which ID to use in a particular app, with the ID generated from the seed phrase. This is far better than using a single Nostr ID across all Nostr apps.
Don't forget, there are not only Nostr apps focused on public notes but also those focused on private notes.
A reasonable chat app allows users to use multiple IDs simultaneously, whereas a microblogging app’s DM often has only one ID. This is just one of the differences between the two. When we say, "Designing a DM for a microblogging app is not the same as designing a chat app," we are not playing with words; we are not that bored.