That's actually a really good point. I've never looked into that, I just took it for granted that to get a line break on HN you need two consecutive newline chars.

I guess the thing to do would be to look at all (well, lots of) comments that have single newlines and see what would break if they were rendered as actual newlines.

Could be applied to all comments made after a certain future date. That way nothing in the past is poorly formatted

Or just brute-force it with string_replace of all "\n" with "</p>\n<p>" and then remove all the empty "<p></p>".

(why yes, i am a PHP guy, why do you ask?)