An update, which just goes to show that Worldclubs access is worth it.

The WC rep in DTW was able to get me back into my original seat on one flight, and into a more comfortable one on the next (important, given that it's an 8 hour flight).

Chisholm was very unhelpful, both by putting me on the wrong track with the original booking (both problematic flights are on KLM, and NW should be clearer that their reservation requests don't always stick) and in being both incomprehensible and unhelpful in their response.

The real zero is the Gate Agent in DTW. Upon discovering the booking problem, I'd been advised in DCA to immediately check in with the gate agent upon arrival in DTW. As I walked past the departure gate for the next flight (3 hours early), I was gratified/surprised to see a GA actually helping a passenger. I got in line.

When it came to helping me, the GA announced "we're not assisting passengers yet" while exiting to stage left. As she sat down with the other sitting GA, she managed to articulate through McDonald bites to "come back in an hour." She then said "you could always go to 43," not further clarifying whether this was in reference to a gate, a phone number, or a former president. As she tucked into her fries, I queried "could I also get this solved at a WC?" She nodded yes, the fries in her mouth accentuating that advice in a north-south motion.

Well, at least she's not flying the plane...