Proven's comment is dead because they are banned. on hackernews banned users can still comment, but their comments start out [dead] until vouched. (comments that get downvoted and flagged enough also go [dead], as do comments deleted by HN mods)

if you have enough karma, you can vouch for banned user's comments by clicking the vouch button, it only shows on the direct page for the comment, you get by clicking the date of the comment.

I know all of this because I am banned.