Proper ruby text (<rb>) syntax support in Markdown

The [rb(rt)] syntax looks nice! The one thing I would like to say is that half-width brackets are difficult to type with a Japanese IME active, necessitating either switching your input method mid-sentence and then back again, or paging through suggestions for a while to get to the correct brackets. For this to actually facilitate comfortable typing, full-width formatting characters will also need to be supported.

I would love to see a common Markdown syntax for this! It would be ideal if that syntax could support a wide range of use cases. W3C has a nice collection of them here: Use Cases - Interlinear Text Layout Community Group