Why did Moshe wear a mask?
Rashi: In honor of the Karnei Hod, so that the people should not gaze at them. (Moshav Zekenim (30) - so they should not benefit from the radiance of the Shechinah constantly.)
Moshav Zekenim citing R. Yehudah ha'Chasid: When his face radiated, Yisrael came to him, and he taught them. When he donned the mask; this was a sign that he finished. Shortly afterwards, he removed it. 1
Moshav Zekenim: This is difficult. "V'Heshiv" implies that he wore it for an extended time!
Why did he not wear the mask when he spoke with the people?