@ theducks, jackie_w, BetterRed and itimpi:
Thank you all so much for your helpful tips! I've been busy with the holidays and haven't had a chance to test them, but they sound promising. You each seem to understand the problem I'm experiencing, so I'm confident your suggestions are pointing me in the right direction.
You seem to be stuck on my mis-use of some terminology and intent on arguing semantics. I wholeheartedly concede that I got some of the jargon wrong, but that does not alter the fact that the problem I describe is real. Bottom line: Calibre will not allow me to produce mobi files with the original rft/traditional formatting. And nothing you've suggested fixes that problem. You're pedantic and condescending focus on my layman's vocabulary is unhelpful. There were a few comments in your reply that suggest you might be starting to grasp my problem... but if I'm not mistaken, your response is basically, "Yeah, that's how Calibre works." In other words, you're merely acknowledging the limitations of Calibre without offering any possible work-arounds. That's also unhelpful. I'm thankful that other people in this thread were able to comprehend my problem offer suggestions, rather than lecture me.