On some modern websites I end up having to select all because the selection mechanism is broken (I'll highlight, remove my finger from the mouse button, highlight another piece of text, and yet the original highlighted text is still totally, or even worse partly, highlighted.). Crtl-A Selecting all and then clicking anywhere is the only way to clear all of the highlighting in these instances.

Thanks for the XKCD. I didn't realize how common this is. Now I'm even more annoyed that so many websites and reader apps force context menus or 'gestures' when you highlight, without a way to disable those context menus or gestures.