UseNewDefaultFont( Enable/Disable ) simply changes the Default Font uses for Print / Text as opposed to Custom Fonts.
Now beyond this TrueType and OpenType Fonts are (generally) Vectored or "Scalable Vector Graphics"... this allows for displaying the font at any size.
Corruption we're seeing here is rare but can happen because of
how SVG Fonts are Processed.
Specifically speaking, it's how the Windows Font Shader works... it is set to UV Wrapping Mode; this means any value outside of 0.0 to 1.0 is wrapped around to fit within these UV Mapping Values.
What can cause the effect being see is specifically a corruption in the Scaling Values for the SVG; and more specifically we're talking about Overlays that "Hijack" the Rendering Context; as they have no knowledge of external variables essential to said Context; say like SVG Scaling Values.
Now if you notice in the image., while most letters are affected, some letters aren't... and consistently we're talking about individual letters in the Font, as opposed to in the Words.
This is because the Font itself is Rasterised into a Bitmap Font when first loaded., this includes multiple sizes; and so it will ONLY recalculate this if you use an "Uncommon" Size.
Something you might've noticed with Modern UI Overlays is that they will not enable for a few seconds after the Application has begun., this is because IF they do it can result in the displayed issues.
As the Microsoft help indicates, a "Workaround" is to simply increase the Resolution Scaling until the Text appears correctly again... but a better solution is NOT to use things like MSI Afterburner or other Overlays that bypass the Post-Launch Hook but instead Hook via the Display Drivers; as this is what causes the corruption as they tend to have their own Scaling Values.
With this said., there is a solution that will ALWAYS work... and that's switching to a Bitmap (pre-rasterised) Font.
Given that most people will be using "Common" Resolutions (720p, 1080p, 1440p, 2160p) even on Mobile Devices., you can reasonably easily construct a Bitmap Font with prescribed sizes and scaling on those resolutions.
It'll use a bit more Storage Space., but will prevent issues like this; and while it will prevent you from using the "Print" Command (which doesn't support Bitmap Fonts iirc) you can still use Text just fine.
