Hello Hans,
\registerhyphenationexception as described in latest languages-mkiv.pdf and i-context.pdf does nothing, contrary to \startexceptions, which behaves as expected. Here is the minimal example:
\mainlanguage[cs]
\showmakeup[discretionary]
\registerhyphenationexception[cs][cíl-em]%
% \startexceptions[cs]
% cíl-em
% \stopexceptions
\startTEXpage
cílem
\stopTEXpage
By the way, what is the reason to print \showlayout on four pages?
Regards,
Jano