I understand that the readme.md was displayed in the past in the Source tab, as Github does, and moved to the Overview tab. In a posting BB made clear that for now this behaviour will not be changed again. This issue is not about this.
What I propose is to render all MD files, when a user clicks on them. One example where you can see such useful behaviour is here: http://goo.gl/EMv2t (links to a specific commit in a Github project) Click on one of the MD files. They are rendered nicely in my browser. This should be the default behaviour for BB too, I propose.