How to make your Facebook and Twitter text bold or italic, and other cool effects

For years I've been using the Panix Unicode Text Converter to create ironic, weird or simply annoying text effects for use on Twitter, Facebook and other plain text-only venues. But now there's a new kid in town, YayText: "Super cool unicode text magic. Use s̶t̶r̶i̶k̶e̶t̶h̶r̶o̶u̶g̶h̶, ????, ???????, and ???? on Facebook, Twitter, and everywhere else." ??????? ??????? ?? ??????????!

Now, like me, half your messages will appear to half your acquaintances as a series of meaningless little empty boxes.