I think I just understood some people's posts:

The inclined-bed thing only has to do with stomach acids. I don't think it would affect most people's breathing.

It may have affected my breathing because stomach acid in my throat caused problems that were aggravated by breathing through my mouth. Slowly, the discomfort caused by the acid's damage taught me to breathe through my nose. Recently, I've woken up with a dry mouth four times. I speculate that it's because it there's less discomfort now from breathing through my mouth. But it may be simply that some allergy clogged my nose in the night.