My thanks and apologies to all: it seems that similarities with an unrelated earlier error on my part--combined with a potentially buggy Media Player Classic--led me to believe the resulting m2ts file was defective as it wouldn't play back audio in MPC: it plays just fine once burned to BD9.
Thanks for all the advice, though: it still helped me to track down the error and to learn about the options and powers that the various programs involved allow me!
I'm having lots of fun using BD-Rebuilder.