<bdo> is a bi-directional override tag, and is typically used with a dir and sometimes lang attribute. This the same as our ve.dm.LanguageAnnotation, except that defaults to just using a <span> tag.
Testing
- Open https://en.wikipedia.org/wiki/User:ESanders_(WMF)/sandbox/nushu?veaction=edit
- Try to edit the contents of the cell under "Your browser/device"
- Observe the text is alienated (highlighted in green and blue stripes)
Expected
- The text is editable (note it is likely you don't have the required font installed, so the text may appears as rectangles)