I might be missing something here. Why would HN care any differently about WhatsApp vs Telegram?

Probably he is referring to that WhatsApp is from a US company vs telegram with Russian origin.

general tendency in HN is Telegram bad, Signal/WhatsApp is good. Even small mistake made by Telegram will be judged harshly, when it comes to WhatsApp, their mistakes are not important.

Yes I am a Telegram fanboy (how can you not like such a beautiful/fast app, in the Electron world where everything takes 10s of seconds to load)

Signal seems like a pretty light/fast/good electron app (on windows at least)?

WhatsApp chats are end-to-end encrypted (even their iCloud backups are). Telegram group messages are always plaintext / available to Telegram, and Telegram 1:1 direct messages are plaintext by default.

Yet they hold the encryption keys to decrypt your chats on the fly. What inspires so much trust in Meta? Especially in a company with "targeted advertisements" as its business?