Not sure. Take a look to the renderer [1] and the source [2]. Link are external for {{{guide-testing-releases.html} test releases}}
I just stumbled upon this in r647420 [0]. After some other tries I figured out:
- {{{foo.html}baa}} is external - {{{foo.txt}baa}} is internal i.e. the linking behaviour depends on the file extension. That's the kind of black magic for which Maven is blamed by users. Benjamin[0] http://svn.apache.org/viewvc?view=rev&revision=647420