what accessibility features are available from the core? is there any recommendation to make the skin compatible ?
Accessibility is a broad topic. For skin development, there is no specific advice that I can give you, that I wouldn't give you for any other web page you were working on, other than if the data is provided by SkinMustache you should probably render it, as there's likely a good reason it's there.
Please see Accessibility guide for developers for some other best practices.