My Reddit clone called Comment Castles [0].

Earlier today I implemented "bbcodes" for bold, italic, underline, em (grey background color) and strikethrough. They way it works for bold is like this: b[text here]. If you want to apply multiple you can go bui[text here] for example, which would be bold, underline and italic text.

[0] https://github.com/ferg1e/comment-castles