Hi
Why do you think it should be allowed? The current rules are arbitrary, but they are quite simple; we don't want to add an ad-hoc exception just for this.
The current rules are already quite complex, I believe there is some thought being given as to how to simplify them.
Out of curiousity, what do you find objectionable about (legal):
function argument argument2 | guard = body | guard = body
as compared to (currently illegal):
function argument argument2 | guard = body | guard = body
Personally, I have no problem with the current way (and would consider anything other than 4 leading spaces in the first example to be evil). However, if you are using a text editor which doesn't automatically indent the start of following lines, it might be a bit more annoying. Of course, if your editor is that bad you should consider changing to virtually anything which isn't notepad. Thanks Neil