I can't be the only one that reads those two examples very differently.
In a first example, the second "occasionally" is stressed, when in second example it feels almost whispered.
In a first example, the second "occasionally" is stressed, when in second example it feels almost whispered.
But what I see from trawling the posts made by narrators, a lot of them do mention that em-dashes are read as interruptions with sudden tonal shift, while cursive implies a non-interuptive tonal shift.
That said, apparently, most audiobook authors actually supplement their own guidance on how to read their books. I haven't found any universal guide yet.