NAMES, PRONOUN USAGE & DESCRIPTIONS
-Always use a transgender person's chosen name.
-Whenever possible, ask transgender people which pronoun they would like you to use.
-If it is not possible to ask a transgender person which pronoun he or she prefers, use the pronoun that is consistent with the person's appearance and gender expression.
The recent Facebook and Tumblr changes enable the third point.
There's kinda three rules for making fun of something and not catching flack for it:
a) Everything is fair game. There are no sacred cows. (Including yourself)
b) Don't make the victim/victimization be the punchline
c) Look in a mirror. (eg, does this look bad coming from you? Think about who you is following/friends with you. Think about what law enforcement would think with only the context of your joke.)
If you live in 'merica then free speech is a free license to hurt people with words. It is never a joke to threaten someone, because that is you making someone a victim, even if you have no intention of carrying out the threat. "It's only a joke" is a cowards defense against taking responsibility for the consequences.
Unless someone presents you with a pronoun/label to use, you're pretty much stuck with using "they" or their name. If they want to treated as an extraterrestrial by picking confusing or unpronounceable pronouns then that's their own business. Don't expect anyone to take those pronouns seriously then. It will always be seen as being a dick to someone if you use a pronoun opposite from what they want. So the safest way is to just use "they", as it has no opposite.