As of October 3 I intend to remove support for quotes around the MathML <ms> element, and the corresponding lquote/rquote attributes.
Chromium and WebKit don't implement that feature.
Bug to remove:
This is a rarely used MathML element, quotes are not part of
MathML Core and not implemented in other browsers and Firefox's
implementation has issues (e.g. bugs 1108608 and 787215).
-- Frédéric Wang