My elderly parents flew STR-JAC and return. Booked through KLM, first two legs on KLM, last leg on Delta. The KLM flight to SLC was delayed (no weather or ATC at the time, just left the gate late), and they missed their connection to JAC. It was the last flight of the day, so they were put on the next day's flight and given a hotel room in SLC. They booked Business, but flew in regular economy on the last leg. KLM (who caused the misconnect) forwarded the claim to Delta, who gave the following response: "...Regarding your seat downgrade, I have forwarded this to our Refunds Department for proper handling. You will receive a separate email from them once reviewed and validated. Additionally, I am issuing a Electronic Credit Voucher for you and your companion in the amount of $xxx each."
They received the E credit voucher, but won't be able to use it (too many misconnects on this trip stressed them out too much, and they won't fly TATL ever again). They never received the downgrade compensation, and aren't sure where to claim that, or who to contact.
Neither Delta nor KLM acknowledged the delay (~18 hours), or paid the compensation due. How can they escalate this?

Can use voucher fir AF/KL flights.

Sounds like they handled the downgrade, not the delay.

They want downgrade compensation in cash, not vouchers. The email indicated that the request was sent to the refunds department. How can they contact them? The E credit was supposed to be "additionally."

Right the voucher ($200) is DL goodwill. The rest of the downgrade (the refund) will be handled by refund department.

It'll be refunded to purchaser credit card. EC261 comp for delay (if qualify) still needs to be done by KLM. Thus they're handling the downgrade, but KLM needs to handle the EC261 delay. I don't know what original message was sent. However it appears agent was only aware/noticed/made aware of the downgrade issue.

Sorry about your experience, but it brings an interesting topic. In my experience, DL is probably the most aggressive among big 3 UA / AA / DL processing too many upgrades in advance.

Each time I had misconnect in paid F in the last few years on DL, I always ended up in coach with plenty people already upgraded on the new flight, so now I just rely on free upgrades or book other airlines or longer connections.

If DL is serious about protecting F customers, they should leave at least F4 seats open until departure time and process remaining upgrades at the gate (of course unless flight is sold out in F). Or they can be a bit smarter about allocating XX seats based on number of connecting F pax from previous flights and predicted number of disconnects.

DL does a good job usually at predictions based on past performance. SLC-JAC is a very short route, with likely no sold F except due to connections from international J.

Makes no sense to hold back more than 1 seat for such route. Also at T-24 F passengers can SDC gor free as long as any seat available. Possible they hold four seats back and 4 F passengers SDC at T-24 (or bit earlier for connecting passengers).

Since the flight was booked through KLM, Delta doesn't have a credit card on file - how can they contact the refunds department at Delta for the downgrade?
The original message to KLM included the story about the delay, but KLM never responded other then by sending the complaint to Delta. How can they escalate the delay complaint?

The card number is part of the eticket. DL just has to pull the original ticket (assuming it was exchanged subsequently) and will have card. They can also hust ask for it.

File for EC261 delay compensation as a separate thing with KLM. Don't mention you already sent in a message. Too many things jumbled together just leads to confusion.

I would expect VERY minimal downgrade compensation in this situation as it will be proportional to the length of the flight segment downgraded. SLC-JAC is 205 miles out of a journey of 5,513 miles, or 3.7%. If the ticket cost $2k rt, the downgrade comp would be $1k * 3.7% * 75% = $28.

It will probably cost the airline more than $28 to process, but I'd request even this small amount anyway as a minor incentive for the airline to avoid downgrades.