(And anyone else having browser compatibility issues...)
Got a reply to my support ticket, and it's the expected bad news:
"I'm very sorry, but out website is no longer supported on IE11, and may not be optimized for Palemoon, or for other less popular browsers. Unfortunately this is not going to change. My apologies for any inconvenience caused.
I understand the sentiment you bring up, but I'm afraid there isn't much that I can do about the issue."
Only selected browsers are welcomed to our store website. That's ONE strange way to sell more games ;)