Yes, very serious. Confirmed in Sitefinity v8.2.5900.0 in Chrome v55.0.2883.87 from 12/9/2016 - haven't tested in Firefox.
Edited to add: The code that's failing suggests using IE may be a workaround. Here are the relevant lines (the second is the one that fails):
Edited to add 2: Confirmed not an issue in IE 11, even though Microsoft announced the end of support for the "MS"-prefixed event object (it just returns the non-prefixed one now). Also confirmed that it is an issue in FF 50.1. In the case of Chrome and FF, the window object still exposes a PointerEvent method, but the document.createEvent method does not support an event type parameter of "PointerEvent".