Due to a limitation in the Markdown renderer that we use -- chjj/marked#44 -- there is no support for the special GFM links (to rev hashes, issues, etc.).
However... like the Marked author, I don't actually care about this feature, and I'm not sure I want it in Markdown Here. This bug is really just a record of our deviation from the GFM spec.
(This issue is forked from adam-p/markdown-here#9.)