I didn't use the Font setting in the constructor, I don't have XP users and I have set Segoe UI in the Form Font, so it would not affect anything.
For Labels where I do not set the text alignment the flatstyle setting works great! Searching the internet gave me solutions like painting the text but that takes a lot of extra code to do, so just a setting is much easier. Thanks for that tip
I already found other weird behaviors, like setting a label to white background color and disable it, then the forcolor becomes blue, whatever your color setting is.
Maybe it's time to seriously dive into WPF...