Re: I detest that
"It does use extensions to determine how to use files though, as do all modern operating systems"
No, it doesn't.
"Double click an image file with html as an extension and see what happens next. Does your OS launch GIMP or Chrome?"
You're talking about the desktop environment here, not Linux. Several DEs started paying attention to the extension in an effort to be friendlier to Windows users, but you can certainly use other DEs that don't exhibit this behavior.