We have a few types of formatting code:
Italics: word
*word* or _word_
Bold: word
**word** or __word__
Bold & Italic: word
**_word_**
Line break:
[br/]
Size: (Changes the size of the word).
[size=4]word[/size]
Link:
[caption](url)
You can use this in the custom welcome message, Announcements, Q&A (both comments and questions), Poll Questions and Answers, and Survey divider text box.
You can NOT use markdown in the Poll footer.