As you may or may not have heard, Facebook is deprecating the XMPP gateway for its Chat service by the end of April. That effectively means that no 3rd party applications will be able to send messages to your Facebook contacts. At least not officially.
Why oh whyyy?
Probably money. Facebook needs to generate some income in order to stay alive. They do that (not only) by selling ads of all kinds. I'd argue that Chat is one of the most used Facebook features and so Facebook is loosing tons of $s if people don't use their own ad-powered products. Seeing every other big player turning away from XMPP, this was also just a matter of time (and in fact this was known exactly for a year).
KDE Telepathy uses the same Telepathy backend as Empathy and possibly other clients, I would assume that starting 30th April, you simply won't be able to connect with any Telepathy client or in fact any client at all. So please don't report that as bugs :) The upcoming KDE Telepathy 15.04 version will not even ship with Facebook account being offered to be created.
At this point, any kind of chatting is as accessible as the Tower of London back in the days; Facebook made pretty good effort to make this as impossible as possible. For example it's impossible to even retrieve a full list of your friends from the API, only those that are actively using the same app as you (which in my case is about 4% of people). Without contacts you cannot send messages obviously sooo....that's a dead end. Personally I wouldn't hold any hopes for chatting on Facebook outside of Facebook (including Messenger).
Is this an early April Fools joke??
Nope. Read the red box at https://developers.facebook.com/docs/chat
What am I gonna do with my life now???
Basically, enjoy the last month of Facebook with KDE Telepathy, have your friends switched to some better service and hold an optional minute of silence in remembering.
Farewell Facebook Chat.