Facebook Messenger allow's text, bolt; italics; strikethrough etc; as per[1], however it only works via "on a computer", ie. not on the mobile apps.
However, I've been using bold text on my iPhone for years because I noticed * this * (without spaces) worked for bold text, but knew people on Android just say the asterisks.
It even claims to have LaTex typesetting!
Anyone know anything about why Facebook hasn't implemented this on their mobile apps?
1. https://www.facebook.com/help/147348452522644?helpref=related