Well, the L1-Support could have said that:

"To report a bug please open the FILE menu, and click on "Send feedback". Ta-dah.

Support is still shit if they can't do that. In a software-company everyone should know the rough path to actually report a bug, or what looks like one.

I have given feedback many times (and on the same bugs) with zero results – I have never received a feedback and the reported bugs are still present … it is less frustrating to use workarounds.

Mea Culpa. I installed 2016 to try and find the issue with my system, I haven't searched around the UI for bug reporting tools, didn't even know Microsoft had added them. Just found it now, indeed it looks quite useful.

I'm going to update my post with more information because actually, there's a lot of great tips from these comments!