Q. Does hyphenation render a diaeresis redundant? Because it wrapped to another line, the word naïveté was rendered as na-ïveté. Should this appear in print as na-iveté?
A. No. Hyphenation imposed at line breaks in typesetting should be regarded as temporary and invisible rather than part of the word. You can bet that if a proofreader were to remove that diaeresis, in the next round someone else’s correction would cause the word to end up whole again. Better to leave well enough alone.