If there are two definitions for a macro with parameters, for example:

macro.hello.HTML    = "<p>Hi, \1</p>"
macro.hello.DocBook = "<db:para>Hi, \1</db:para>"

Then qdoc ends up in an inconsistent state when parsing

/*!
  \page test.html

  \hello {world}
*/

because it tries to read the arguments twice (for each macro) from the input stream, regardless of the selected output formats, and obviously fails on the second round.