The following mwe

\definefontfeature[fraction][frac=yes]
\definehighlight[textfraction][style={\feature[+][fraction]}]

\starttext
a fraction \m{\frac{1}{n}}, \textfraction{1/n}, \vulgarfraction{1}{n} in
the text
\stoptext

works for all but \textfraction in the latest beta (luatex, luametatex).
Has something changed or have I missed something?

Alan