https://www.wanikani.com/chat/api-and-third-party-apps/4024#post105###

Here are the supported markups:

#rad#text#/rad# = Radical highlight (blue)
#kan#text#/kan# = Kanji highlight (pink)
#voc#text#/voc# = Vocabulary highlight (purple)
#read#text#/read# = Reading highlight (black)

**text**, __text__ = bold
*text*, _text_ = italics
[Link Text](http://www.google.com) = hyperlinked text
 = image
~br~ = break (i.e. new line of text)

(Additional markup info: https://github.com/showdownjs/showdown)