For what it's worth, the Tabbed Navigator does the right thing with the same content (two or three paragraphs, with other tags, like <strong>, in them). Perhaps, then, this is just an accordion navigator issue.
Unfortunately for me, the tabbed navigator just won't meet my needs in this case (I have phrases for the click-on-me names of the panels, and the tab layout doesn't have room for them). :-(
Is the Git repository for the current Xerte code accessible, so I could maybe pick up this fix once it's made? All of the repos I see on GitHub seem to be for old versions.