[nvartolomei]

This made me think about the case of mobile network operators recycling phone numbers. How does WhatsApp handle that? What about Telegram which isn’t e2e encrypted and stores everything on their servers by default?

There are operators recycling numbers after less than a year of inactivity/zero balance on pre paid SIMs.

[mcraiha]

You can enable two-step verification to "lock" your number. But yeah, using phone number as your platform ID is a very bad thing (security and privacy wise). https://faq.whatsapp.com/general/verification/about-two-step...

[trollitarantula]

Telegram by default deletes all data after 6 months of inactivity. You can also set a password and configure two-step verification.

[noxer]

There is no way to confirm this claim so its as good/bad as whatever all the other providers say. Personally I think they are more likely to actually care and delete the stuff properly because they have no use for it and it costs them serious money to keep storing it. But that's just a opinion.