Animation is broken on .NET4.x Scripting Backend when using German locale

(this is especially @thierry_unity, but I think the discussion should be open)

Since the forum keeps locking the animation bug posts I make (without the actual bugs being fixed), I'm now not sure where to post this since it affects Animation, Timeline, the Editor, Serialization, ... Feel free to move the post to a better place.

(the original forum threads were https://forum.unity.com/threads/tim...-and-undocumented-behaviour-continued.531997/ and https://forum.unity.com/threads/timeline-animation-bugs-weird-and-undocumented-behaviour.526500/)

Finally today, after lots of blood and tears and screaming and trying to figure out where this madness (us not being able to properly animate since the release of Unity 2017) is coming from, I was able to fully reproduce the issue.

It boils down to being a combination of using .Net4.x Scripting Backend, which in turn causes the Editor to use our german locale instead of cultureInvariant as it did with 3.x, which in turn breaks animating values.
I wrote some more details here: https://forum.unity.com/threads/editor-is-using-windows-locale-settings.442847/#post-3605840

I just made a new bug report, because this is really seriously affecting us (we can't animate anymore using .Net 4.x!)
Case 1073448

Unity is planning for a while now to make 4.x the default scripting backend, but when you do that you'll basically break animating for every user with german locale.

I'm still very surprised nobody else has reported that issue, as it is consistently affecting all people in our team for months now, with workarounds and hacks being used to work around it, across various machines and cities.