I'm getting back into the swing of things now with travel picking up for me. The scenario I'm running into is I did get what I consider the appropriate "nights stayed" credit when I had two rooms on the same date though on separate reservations, but I'm only seeming to get half-credit for a couple of other reservations where I had two rooms under the same confirmation number. Is this appropriate? Or would it be possible to call and ask for the "extra" nights...as well as staying away from the two rooms on one reservation scenario?

You can't earn 2 elite night credits for booking 2 rooms. 1 elite night MAX per calendar night.

In addition to what craigthemif mentioned: You can only get points on two rooms if they're billed to the same folio per the Honors T&Cs -- technically if you have two overlapping reservations you only get any credit for whichever one posts first which can (could?*) make certain scenarios tricky-- like if you're checking out of a property on one day and have an early flight into the next city for the following day -- one may be tempted to book an early night at the 2nd property to be sure you can get to a room on arrival -- but if you do this nothing will post for that stay [though the Diamond Desk has extended a courtesy on a couple occasions]

I would guess if you're seeing night credit for overlapping stays that's a coincidence (like nights rolled over from last year or one of the promos that gave double night credit) rather than actually getting credit for both reservations.

(*- With my current point balance and having Lifetime Diamond I'm not sure that I care as much at this point...)