Comment by KeytarHero

Yeah, this is my theory too. I use Tinfoil for Facebook on Android, and it shows I have 15 unread messages. Basically, every time I open Tinfoil while I have a new message I haven't read in Messenger, it increments, and that never gets cleared. If they were trying to drive engagement or to get you to install Messenger, why would they want the number to keep increasing well after you've caught onto the trick?