Hallo Patrick! After a short break, I would like to continue learning context. Have you got any answer to your question?

...

another solution is to make a specific font handler (like the hanging one) for a class of fonts like cmr, in that case you can link such a handler to for instance a cmr10 font (see hand-*)

I have tried that, but with strange results:

\startfonthandling[cmrfix] \definecharacter quotedblbase {,\kern -.1em,} \stopfonthandling

%\setupfontsynonym[Serif][handling=cmrfix]

\setupbodyfont[14pt] \starttext \mainlanguage[de] \startquotation To \TEX\ or not to \TEX. \stopquotation \stoptext

The definition of quotedblbase in line two is used without even activating the cmrfix font-handler. How do I use the handler properly?

Patrick