I find thematic break a poor choice on at least three levels:
- Theme is overloaded with an unrealed meaning in other technologies (WPF/Silverlight/XAML themes are analogous to CSS).
- Break is overloaded with a different meaning in both HTML and CommonMark. How does one produce a soft thematic break?
- Too many words are used to denote a simple unambiguous concept.
If I were asked to propose an alternative term, my suggestion would be boundary.
Having said that, I do agree that horizontal rule should have been replaced due to its presentational semantics. In fact, an abovementioned project of mine had used *** (or --- or ___) for topic boundaries before CM’s sudden (for me) change in terminology.
I simply fail to see any good reason for rejecting unordered lists while embracing thematic breaks.