I'll use a lot of .md files coming from various places, e.g. done manually myself in some editor, from ithoughts, form some github sites, etc. Usually view them in marked2 but when I want to edit I need get to the actual source file and open it in an editor.
so for me it would be quite useful to be able to just request it being opened in some "default" editor I can set up out of the application instead of from finder. Guess that's not precisely the same request that James had but it is on similar lines.