Currently, in the Text Format Properties, it is possible to set a configuration that isn't aligned with what a particular font file(s) offers.

For example:

The Windows Default Font "Arial Rounded MT". This font is technically a 'Bold', and doesn't contain any Italics versions, can be set in Studio as:
Font Family: Arial Rounded MT
Weight: Thin
Style: Italic

However, there is no such thing as an Arial Rounded MT Thin Italic -- therefore, it creates a mismatch between the Properties/XAML values, and what is visible on-Stage.

Repro Steps:

1) Ensure that the 'Arial Rounded MT Bold' font is located in C:\Windows\Fonts.

2) Open the DashMoto Sample, select the large Speedometer numbers in the centre of the screen, and change its Font Family Property to 'Arial Rounded MT'

3) Change the TextBlock's 'Weight' and 'Style' Property values.

Observe how none of the value selections create any change in the representation of the text on-Stage.

Expected Results: Studio 'filters' available Text Properties to what is available for each Font Family.