[pwg]

> you never know when you need to write https://

It is not a proper URL without the protocol part up front. Browser creators improperly trying to hide the protocol not-withstanding.

> just happened to me: in a youtube description you cant just put ycombinator.com,

ycombinator.com is not technically a URL, it is simply a domain name. The fact that browsers all invisibly 'auto convert' it to a URL when entered into their URL/magic bars does not magically make it into a url. If youtube's code which is looking for URL's to automatically make them anchor links simply looked for words with dots, then a large amount of false positives would occur (things that are not URL's getting wrapped in anchor links).

You can blame the browser makers, and the evil one specifically, for all the hiding of URL structure such that people now think "ycombinator.com" should be interpreted as if it were a URL everywhere.