I was commenting on a Google Doc tonight and wanted to put some emphasis on a word, so I put two asterisks on either side, so it looked like this. After hitting Comment, Google applied bold formatting to everything inside the outermost asterisks, so it looked like this in the comment:
So to add bold to a comment, place the content to be bolded within two asterisks. To italicize it, use the underscore. The two formatting examples above looked like this when I typed them:
Did not know you could put asterisks around things for *bold*... Does underscore _italicize_?
You can also use hyphens for
strikethrough (-strikethrough-), and to mention another person in the document, precede their email address with a +, like [email protected]