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Your example is (unfortunately) far too complex for me to answer
your substantive question, but the sub-question "Why does
\hyp[h]enation {<i class="">word</i>} inline [cause] the whole <i
class="">word</i> [to] disappear ?" is much easier to answer. <br>
<br>
\hyphenation {<word>} tells TeX how to hyphenate subsequent
occurrences of <word> in the text; it does not expand to a
word with valid hyphenation points embedded but rather expands to
the empty set.<br>
<br>
Philip Taylor
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