In case you use TextFormattingMode.Ideal vs the TextFormattingMode.Display that is the default, you get a pixel wide space in the Menu/window Header, visible mainly with colorful themes.
While not critical, it could use some improvement in order to have the gap filled.
you can force it in line 504/TestContent.xaml.cs
TextOptions.SetTextFormattingMode(window, TextFormattingMode.Display;
Environment
- Fluent.Ribbon: 11.0
- Windows 11
- .NET 4.8

In case you use TextFormattingMode.Ideal vs the TextFormattingMode.Display that is the default, you get a pixel wide space in the Menu/window Header, visible mainly with colorful themes.
While not critical, it could use some improvement in order to have the gap filled.
you can force it in line 504/TestContent.xaml.cs
TextOptions.SetTextFormattingMode(window, TextFormattingMode.Display;Environment