R is definitely deep discount economy for KL marketed flights. Sure looks like a fare or filing error. DL uses R for FC/PE award bookings. Note that ITA is not perfect. It still messes up on married segment bucket availability when you use the multi-city search feature (it will incorrectly quote fares based on individual flight bucket availability rather than looking at married segment availability when multiple segments are involved on a single fare).
Yep. The above looks like an error/mistake/incorrect quote that then is treated incorrectly when ITA is pushed over to DL.com via PowerTools.
Alas-- I'm not seeing a way to split a PS fare with an economy fare, which in my situaiton, would be quite fine; using PS on the outbound is forcing me to use a W on the inbound, when I'm 92.5% or so likely to get that via upgrade.