I guess the first question to ask is how much control do we want to give developers over how their app is presented in the store. We want to give them enough control to describe their app well, but we also want some level of consistency so that we can present the information in a useful way in multiple contexts (command line, graphical package manager, web, etc).
Looking at Android, it seems that it has support for bold text and linkifies things that look like domain names or urls. Apps seem to use various unicode characters to simulate bulleted lists. Images are restricted to the app icon, and a set of screenshots and videos: all of which are displayed in the same location for each listing. The iTunes store seems similar, although I haven’t really looked at it in detail.
As far as links go, it would be good if we could avoid things like the following:
Visit [www.trusted.com](http://www.malware.com) for more information.
So maybe we don’t want full markdown-style links?