\definefontfeature[default][default][expansion=quality] \setupalign[hz]
\setupbackend[export=yes,css=yes,xhtml=yes]

\unexpanded\def\,{\mathortext{\mskip\thinmuskip}\narrownobreakspace}

\starttext
  \startbuffer
    narrow\,nonbreaking\,space
  \stopbuffer
  \getbuffer \par \dorecurse{10}{\getbuffer}
\stoptext

