You may prefer one or the other but most would admit they are pretty similar its just that the former hasn't needed an entire new language inlined into it. Given JSX has all its angle brackets, end tags and escaping expressions with {}, it can actually be more verbose.
Nesting dozens of items is fine. That single line was more of an HN comment format limitation. This might be a better judge of readability:
C#
http://imgur.com/a/nVWdC
JSX
http://imgur.com/a/qwAfD
You may prefer one or the other but most would admit they are pretty similar its just that the former hasn't needed an entire new language inlined into it. Given JSX has all its angle brackets, end tags and escaping expressions with {}, it can actually be more verbose.