What would cause click events to stop working in Internet Explorer 11?

In case anyone else stumbles upon this: The problem turned out to be a bug specific to IE 11 for Win 7/Server 2008 R2. It doesn't happen in IE 11 for Win8.1+ or for any other browser.

Here's more info on the bug: https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/205775/

I "fixed" it with one line of CSS:

use {
    pointer-events: none;
}