Or am I doing something wrong?

With the following, Schwarzenegger is not hyphenated according to the 
instruction. I get:

    \mainlanguage[en]
    \hyphenation{Schwarz-en-egger}
    \startexceptions[en]
    epi-graphs
    Mount-weazels
    Mount-weazel
    \stopexceptions
    \starttext
    \hyphenatedword{Schwarzenegger} \\
    \hyphenatedword{Mountweazel} \\
    \hyphenatedword{Mountweazels} \\
    \hyphenatedword{epigraph} \\
    \hyphenatedword{epigraphs}
    \stoptext

-- 

Rik