I booked through the AMEX portal about a week and a half ago with the "vanilla" platinum since I already hit the$60k with AMEX Reserve and the ticket issued did not have a C+ "upgrade" which typically occurs after booking, I waited a couple of days and then realized that AMEX did not have my Skymiles # added to the reservation even though it's in my AMEX profile and Delta's system did not pick up on it either but I cleared for the C+ "upgrade". This forum reminded me to use my RUCs and I am now cleared in F from OAK-SLC-ORD and back. See some of you at the conference!!!

The issue wasn't the exit row. Every seat we tried to pick (rows 5-9) gave the same exit row message. There are no exit rows in C+ on the CRJ900. She was assigned 6C but was unable to sit by the window in 6D. We also tried 7C, 8D, 9C, etc., all generated the same exit row message. That explains why she wasn't automatically upgraded with the lap infant into C+. But it doesn't explain why every row of C+ is coded as an exit row, when the only actual exit rows are 12 and 13.

IIRC the extra oxygen masks for lap infants are only present in every other row and of course only one lap kid is permitted in each such row.

This would mean that the CD seats in rows 6 and 8 are the only suitable ones in rows 5 through 9 inclusive, and if there's already a lap kid in row 8, your baby must fly in row 6 of C+.

I don't think this is true, or it isn't monitored.
Same PNR, 2 adults, 2 under 15. I put 1 adult in exit row, other 3 behind or in front of exit row. I wasn't aware this was not allowed when I requested it, nor did Delta stop this and we have flown this way on multiple flights. I have even done the 2 adults in the exit row, and 2 under 15 behind on the a330 2-4-2 layout.

It's not allowed because in an emergency, a parent (or other relative, guardian, etc.) sitting in that exit row would make saving and taking care of their kids top priority and go to the kids rather than fulfilling their crucial emergency exit row duties.

Being able to get away with this doesn't make it right. You're potentially compromising everyone's safety (and possibly their lives) for a couple more inches of leg room for your own personal comfort.

I wasn't asking your opinion on why, just show me the rule. I honestly wasn't aware of it, I wasn't purposely trying to "get away with it". My example is to show in context of this thread that the seat selection will allow it and Delta employees aren't checking.

In an emergency, those kids in the next seat need off the plane regardless. One could easily argue this isn't compromising and those human lives are just as important as any other soul on board. One could argue that for any family members you would show preferential treatment. However my intent wasn't to argue should or not. Just trying to understand what Delta's official stance is.

All the AB seats in C+ and Y are off limits with a lap infant, because there are only 2 masks on the left side of the plane. However all the CD seats (other than exit rows) should be in play. The fact that my wife couldn't select any CD seat in rows 5 through 9 shows there was some kind of tension between the lap infant status and the way Delta designated those seats on the plane. There were no other lap infants on the entire plane. I've never seen this before, including when we've traveled with a lap infant on the same aircraft.

Did some research, closest thing I could find is "must not... Have a condition or responsibilities, such as caring for small children or pets, that might prevent them from performing the applicable functions"

Having a 10 year old sitting in the seat behind you does not count as caring for a small child that would prevent you from performing the exit row functions.

I cannot find any evidence to corroborate the statement in bold. I think you took a pretty big leap from the actual guidelines. Not to mention the evidence I presented that Delta's system nor employees question or prevent it.

But again, please provide proof to correct me.