Yes, FB messaging is XMPP, and whether your client tells fb or not obviously depends on your client, specifically whether it implements XEP-0184 (still in draft) or not:
Sorry, didn't mean to be rude. I meant that it was obvious that it was up to the client to send read receipts or not (you could easily just take an open source XMPP client and comment out the line that sends read receipts), not that the relevant XMPP draft was obvious.
