Overall, it is used by opposition parties in countries like Russia, Belarus and Iran for day to day stuff, so it is fairly secure

I think this is overselling the "privacy" aspect of storing your personal messages on a server where the admins have complete access without you ever knowing if/what they're doing with it.

Make no mistake, Telegram is as "private" as Facebook. They have access to all your data and as that data grows, it grows in value. It's only a matter of time before they directly or indirectly exploit this (or get compromised) and all your "privacy" is out the window.

No hate towards Telegram, I'm sure its a great platform, but people should at least be aware that it's basically the Pepsi to Facebook's Coke.