[AnonC]

> Unless they're reading my facebook messenger messages, I have no clue how they would have discerned that piece of information.

Facebook Messenger is not end to end encrypted, unlike WhatsApp (which is, but shares metadata with Facebook). Of course it’s reading your messenger messages as much as it’s reading posts on Facebook to see what the content is about and how to use it to build a better profile of you to show you and your contacts more “relevant ads”.

Consider Facebook Messenger like a private closed group on Facebook. Just the interface and conversation models are different.