[reader_1000]

> I'm not sure how easy it is to figure out whether those 'highly forwarded messages' are all the same, or somehow link them without knowing anything about their content or linking them to information you already know about people.

They use a counter. I don't know, however, if it is enforced on only client side or it is in a unencrypted metadata which can be checked on server side.

> Forwarded messages contain a counter that keeps track of how many times a message is forwarded. [1]

[1] https://faq.whatsapp.com/general/chats/about-forwarding-limi...