Thank you for summarizing my assumptions, but it was not fully correct: - I'm not saying backdoors are "routinely" detectable, I'm simply saying it's possible

Thank you for summarizing my assumptions, but it was not fully correct: - I'm not saying backdoors are "routinely" detectable, I'm simply saying it's possible to detect them. In contrast, we have zero possibility to find out if Telegram is doing something nasty with your chats. Telegram may well do it already, and we may never learn. - Regarding the incentives - security researchers often disclose vulnerabilities to the public. Obviously they have the incentives to do it. As for the optional nature of Telegram E2E encryption - Signal and WhatsApp successfully demonstrated it's possible to make E2E the default (and only) option. There's no competition here. I wonder what proportion of Telegram users understand the ramifications. Many people migrating from WhatsApp to Telegram probably don't.