We can use facebook in Nepali using Google Input Method – Google Transliteration IME for Nepali Language Input (while using Unicode Nepali option is still there)
Read our article here for details: http://techsansar.com/nepali-it/using-google-input-method-google-transliteration-ime-for-nepali-language-input-1736/
This way you can write Nepali words (unicode ones) in almost all websites and applications.