On a more constructive side, I think adding some value by giving the poster some feedback or engaging in a conversation about the topic would be nice, otherwise it just sounds as an attempt to show off.
I'm not a fan of these "header only" projects nor am I a fan of overly clever code because even though it's fun and rewarding to write it's not a great fit for larger or collaborative projects where consistently adhering to a coding style (hopefully one of the secure ones) and favoring readability over "coolness" are the way to go.
People love to blame C for all of its footguns but not a lot of people like to write "boring" code which kinda sucks...
Please don't take this personally, even though I have to admit that I felt somewhat irritated upon reading your comment it is my no means my intention to attack you with this rant.