RTL text appears to use a margin too far to the right (eg. outside of SVG clipping region. See the two rtl examples in the referenced W3C test.
The problem is not RTL per se but rather the text-align property. If you set text-align to left explicitly on the rtl example, they render correctly. On the other hand, setting text-align to center or right on any text moves it too far to the right. I don't know what (if anything) text-align should mean in SVG, so I have no idea about how this should be fixed.
Closing, this was fixed as a byproduct of the text fixes from late last year.