Trivia

Well, a webserver is free to use any character after the leading URI part for whatever purpose it wants.

That being said, the use of ~ generally hearkens back to the early days of the web, when just about every web server ran on Unix. In the Unix world, systems supported multiple users, each with their own home directory. If you want to go to your own home directory, you cd ~. If you want to go to some other user like fred 's home directory, that would be cd ~fred.

So when people started putting up web servers, they would generally let every user in the system have their own web space, which is accesible from the root of the webserver by using ~username.

For example, a very old website of mine (now defunct) provided by an old ISP (Telepath) was at http://www.telepath.com/~dennison/

Damn, you forgot mentioning the "public_html" dir. ~user/ content was generally served from /home/user/public_html/ directory…​ Good old days :)