Markdown renderer fails to handle certain links (BB-10248)

https://bitbucket.org/tlroche/lightningnox/raw/238e6f9c19aa1211bcff81fda1b45d3df7f75157/README.md and its predecessor https://bitbucket.org/tlroche/lightningnox/raw/eae1d18b45457c1166ac30f5434760fc376a68d0/README.md each define and use the link

[R @ wikipedia]: http://en.wikipedia.org/wiki/R_%28programming language%29

as well as very similar links, e.g.,

[bash @ wikipedia]: http://en.wikipedia.org/wiki/Bash_%28Unix_shell%29

The BB markdown renderer "does the right thing" with the latter definition-and every other link in the file!-but refuses to render the former. And unless I'm missing something, there's nothing wrong with the former. Am I missing something?