My Kindle DXG does not hyphenate either, however I do notice that if the word spacing is too large it has some kind of algorythm to keep the full justification from pushing all the way to the right side margin. You can see an example of this in the attached screenshot (look for the red arrow). At first I thought this was an anomaly, but I see it occur every few pages. This is certainly better than nothing, but hyphenation would be much better.

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