Open
Description
This is described in https://mathml-refresh.github.io/mathml-core/#opentype-features :
If on the element the CSS property direction is rtl, then user agents must enable the rtlm OpenType feature on text nodes [OPEN-FONT-FORMAT] unless it contradicts what the page author has specified with the font-feature-settings CSS property.
and in https://mathml-refresh.github.io/mathml-core/#radical-symbol :
The radical glyph is the glyph obtained for the character U+221A SQUARE ROOT, applying the rtlm OpenType feature if the CSS property direction is rtl [OPEN-FONT-FORMAT].
I think we need more experiments / tests for these.