This site offers one solution: by replacing the characters themselves with unicode equivalents, you can format text anywhere.
β₯
This is some example text showing all the different formatting options offered.
π§π΅πΆπ πͺπ΄ π¨π€π’π eΜΆxΜΆaΜΆmΜΆpΜΆlΜΆeΜΆ πβ―ππ ππ΅πΌππΆπ»π΄ π’ππ π©ππ dΜΆiΜΆfΜΆfΜΆeΜΆrΜΆeΜΆnΜΆtΜΆ π»β΄πππΆπππΎπβ πΌπ½ππΆπΌπ»π π°π§π§π¦π³π¦π₯.
However, if your users don't have a font installed that has the various characters available, they might see little boxes or question marks instead.
http://www.gschoppe.com/projects/fbformat/