Add support for (custom) syntax-highlighting for fenced code blocks in MarkdownTextBlock
But that would be beyond what the control *should* do in terms of separation of concerns.
That's why MarkdownTextBlock could offer a way to register some kind of callback function which is called whenever the control comes across a fenced code block with a specified language ID. The function would get the original text and is expected to return either XAML objects or maybe a more abstract of representation of colored text which is then handled by the control.
This was added in 3.0. A developer can provide a custom renderer and provide their own rendering or use the built in syntax-highlighting.