Created attachment 206904 [details] Test case Use the attached test-case. The auto-height regions with left-to-rigtht block direction are incorrectly setting the logical-height when the flow thread is in top-to-bottom mode.
We should instead set the logical-width of the region when the flow has different block direction than the region. We could also ignore the writing direction of the render regions when computing the styles and avoid having such issues, but that would also affect the logical-width / logical-height CSS properties.
CSS Regions were removed in Bug 174978.