Hi,

I discovered this bug while answering a question on TeX.SX. Consider:

\define\cyrdash{\dontleavehmode\scale[sx=0.80]{---}}
\unprotect
\setuplanguage
[\s!ru]
[
    \c!midsentence=\cyrdash,
    \c!leftsentence=\cyrdash,
    \c!rightsentence=\cyrdash,
]
\protect

\setupbodyfont[dejavu]

\starttext
Normal text|<|English

\mainlanguage[ru]
Normal text|<|Russian
\stoptext

The pdf shows:

Normal text—English
Normal text„Russian

Why the quote instead of the emdash. The output is okay is if \mainlanguage is set before |<| is used for the first time.