Why not just use markdown? There's no chance of messing up the escaping, and there's no knowledge of html required for your commenters.
Want to make something italic for emphasis? Encase it in asterisks. Want to make it more emphasized? Encase it in two. Links are reasonably simple, too (if you decide to allow them). Quoting someone, either indent it by a few spaces or put a > char in front of it, depending on the implementation.
Or skip markdown and use wikitext or bbcode.
It's easy for you, it's easy for your site visitors.
Want to make something italic for emphasis? Encase it in asterisks. Want to make it more emphasized? Encase it in two. Links are reasonably simple, too (if you decide to allow them). Quoting someone, either indent it by a few spaces or put a > char in front of it, depending on the implementation.
Or skip markdown and use wikitext or bbcode.
It's easy for you, it's easy for your site visitors.