@WhiteNoise I apologize. I wrote clinically to belie my intense frustration. I have the sense that my frustration was evident nonetheless.
I love Obsidian, especially the Live Preview feature, but I also get extremely frustrated by its UX at times. I realize that Live Preview is still somewhat young, as a feature.
As a long time software developer, I prefer keyboard interactions to mouse/tap interactions enormously. I should have reported these bugs sooner but instead I waited until they were contributing non-trivially to my stress level.
In this case, this particular bug seemed tractable. Perhaps it is owing to several smaller issues in how Obsidian Live Preview handles packing/unpacking blocks of formatted text. It stands to reason.
To go forward I will attempt to note where I encounter these issues.