I did get an answer to a follow up question directed to support. It was one that was directed as a bug-report that didn't. So I'd suggest using the support link rather than the bug-report link.
And for reference, I was having problems adding an amex card, getting weird failure notices that were clearly due to some backend coding issues, but that seems to have been fixed recently. They now accept US based Amex cards, but not Canadian based Amex cards, so its still rejecting my Amex, but, at least it now gives a useful / meaningful error code, saying "tender type not accepted" or something to that effect.