I tried to construct a link like this:
[goo](http://dictionary.goo.ne.jp/leaf/jn2/9174/m0u/いい/) and it caused the Markdown parser to produce goo, which (if you're reading this in the future) is not actually a link, just the word goo.
I was able to fix it by URI-escaping the いい like so:
[goo](http://dictionary.goo.ne.jp/leaf/jn2/9174/m0u/%3044%3044/) which produces the correct goo.
but it'd be great if the parser could characters outside ASCII, since Japanese is going to be using a lot of them! Not to mention, I doubt most nonprogrammers would be able to reuse this kind of fix.