I said:

Interestingly, if I forget about unicode and use é instead of é, then no matter what I put in the preamble I get the e with a guillemot superimposed. So whatever is mapping é incorrectly seems also to be mapping é incorrectly.

Further testing suggests that my problem is this: Between \startXMLdata and \stopXMLdata, where MathML is being parsed directly by ConTeXt, I get the wrong results for accented characters within <mtext> elements. For example, I get an e character with a guillemot superimposed on top when I want an e with an acute accent. It doesn't seem to matter whether the markup is unicode é, the entity é, or the command \eacute. Similar problems happen with other accents I have tried. In the case of ñ the accent is almost right but comes out too big (looks like the maths version of the accent?). The following is my local test file, using unicode and comparing running text to <mtext> in MathML: -- \mainlanguage[es]\enableregime[utf]\useencoding[uc] \usemodule[mathml]\setupoutput[pdftex] \starttext Situación niños volúmenes sí interés: \startXMLdata <formula><math><mfrac><mrow><mtext>Situación niños volúmenes</mtext></mrow><mrow><mtext>sí interés</mtext></mrow></mfrac></math></formula>\stopXMLdata \stoptext -- The following is a non-unicode test file that will process on Live and exhibits the same errors in the MathML accent rendering. It uses entity references instead of unicode in the MathML, but because they map to the same thing the output is the same: -- \mainlanguage[es]\enableregime[utf]\useencoding[uc] \usemodule[mathml]\setupoutput[pdftex] \starttext \startXMLdata <formula><math><mfrac><mrow><mtext>Situación niños volúmenes</mtext></mrow><mrow><mtext>sí interés</mtext></mrow></mfrac></math></formula>\stopXMLdata \stoptext -- I have a feeling I have made this more complex than it needed to be, but can anyone shed light on how to fix it? Thanks, Duncan PS Apologies for the nonsense Spanish content - it's just random words with accents.