Dear Hans and Wolfgang
Thanks for these - I had discovered the hyphenation explanations on WiKi but was still getting odd effects, with the emdash plus following word sticking out at the right (though this was alleviated by adjusting tolerance and stretch). I'll keep watching for this but in case of difficulty I can always replace --- globally with something like \Emdash, defined as:
---\hskip 1sp
It's more of a puzzle that ConTeXt allows hyphenation of an already hyphenated expression - I hadn't encountered this before with iterations of plain TeX so had never given it any thought. Any particular instance is easily suppressed as you indicated (or by putting the bit after the hyphen in an \hbox), though one then has to check that there aren't any unforeseen consequences elsewhere in the paragraph. But it's not exactly a huge problem!
Best wishes
John 🇪🇺 Слава Україні! 🇺🇦
