As of now, short url points to a particular wiki url, not to a particular page. This means that if a page is moved without leaving a redirect, the short url breaks. I'm not offering examples since I confirmed this from the Panda's (YuviPanda's) mouth.
I consider this a major bug (and if I'd known about it before deployment, I'd have considered it a blocker).
The whole point of this extension is to provide short urls for indic (and other) wikis which can be used outside of the wmf projects on the internet for linking to wiki pages without the hassle of the terrible unicode encoding. I don't see how that's possible with short urls breaking with every page move since that means that if a person uses a short url today (e.g on facebook to say he created! a wikipedia article) and an admin moves the article without a redirect (to conform to a naming guideline or something), the person's facebook status would effectively break since the url would point to a deleted page. It is also possible that said person is embarrased/annoyed enough to never return to editing wikipedia.
I think it is reasonable to expect these links to be permanent in nature so that they can be used on the web without the fear of going kaput in a few months.
Version: unspecified
Severity: major