[Nvn]

That's actually discussed in the bug report[1] and apparently its use is discouraged by Unicode.

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=740477#c2

[nemoniac]

Unicode has a gazillion code points and it's discouraging us from writing our own language? Really?

[Someone]

http://unicode.org/faq/ligature_digraph.html:

A: The existing ligatures exist basically for compatibility and round-tripping with non-Unicode character sets. Their use is discouraged. No more will be encoded in any circumstances.