I do need to clarify how the template parameters and twig expansion works, I admit. In the development version that I'm working on I've refactored the template parameter code to allow other preprocessors than Twig, so now would be a good time to rewrite the documentation.
For now I don't have a solution to your wish to display the test description highlighted. But I've just updated the code in the development version so that it allows the use of '%h' column format specifiers (i.e. raw html) in the "For example" table as well as the result table. The development version also allows you to define Twig macros in the prototype. The combination of those two features should allow you to format your tests in a better way. But you'll have to wait another month or so :)