When you are writing a comment, there is a "Show help" button in the bottom right corner of the text box. It normally shows the codes for bold, italics, links, etc. Now it is not working for me for some reason.

Bold and italics are done enclosing the text to be formatted with one asterisk and with two asterisks on each side, but I never remember without looking which uses one and which two. Let's see: One asterisk on each side, Two on each side.