Leniency in journals' paper structure "guidelines" (required sections and divisions) I have observed in the "author guidelines" of journals, that results and discussion may be requested as 


distinct "results" and "discussion" sections, 
or as combined "results &amp; discussions".  


In particular, more qualitative observation based topics tend to prefer the latter, while direct quantitative measures that may be the dominant tool in the field may be the impetuses of choosing distinct sections.  

Has anyone had any experience with journals and just how rigid they may be when it comes to the hierarchical distinction/formatting of results and discussion sections?  

My thoughts are that a journal may be more willing to separate the sections than to combine. But I am trying to gauge whether it will even be worth approaching the journal to inquire whether they would consider a manuscript with a combined "Results &amp; Discussion" sections.
I hate it when a journal decides to stretch you on a Procrustean bed of arbitrary structure, since many research projects simply do not fit on such.  Some really want you to fit their arbitrary structure, while others will bend, and it's not really possible to know which is which and how much flexibility you've for unless you talk to an editor.

That said, I've often found that with a little bit of mental gymnastics in how you approach "results and discussion" you can generally make things work.  Consider, for example, this decently-cited paper of mine, which didn't really fit the "intro - results - discussion - methods" format desired by the journal, since it was about a (fairly complex) method.  Well, if you think of the method as being the result, then we essentially shove the whole paper as we wanted to structure it into the "results &amp; discussion" section, with our preferred structure as subsections.  The "methods" section then contains all of the boring details about protocols for the validation tests that we ran.

Bottom line: often a journal really means it about its structure requirements, but that actually constrains you less than you might think.