HLS is supported by default on Safari (on MacOS only, AFAIK). HLS is developed by Apple so it make sense to support it natively on their products. There's a bunch of players that has "HTML5-first" support, it tries to use <video> tag and if the browser doesn't support it, it fallbacks to flash.

That's so weird, why would the comments of all things require flash!?

Probably because it's easier than long polling and more widely supported than web sockets.