agree, but still signal is a platform based in US and with ~10s million $ yearly costs, they already makes some dangerous choiches like launching a shitcoin. It could be compromised and we would remain without decent alternatives (fallback on mail+gpg?).
We need nostr based pravate dm to happen. 

 And people building beyond that already.
https://github.com/nostr-protocol/nips/blob/master/17.md