Any thoughts about changing the default fonts?
You can already change fonts in this style. I put 'Futura' as the default, but you can type whatever you have there. Or do you mean something else?
Is it possible to do more extensive Markdown support?
Yes, but I don't know if I'll have the time to make a whole 'parser'. The one on Hubski is actually quite extensive and I only deciphered bits of it that I used for testing.