“Tony Moran wore the mask.”
Wrong
Correction
Moran played the unmasked Michael for a few seconds. Nick Castle wore the mask.
Castle wore the mask for most masked scenes. Moran, credited "Michael age 23," is the face in the unmasking. Wallace wore it in the closet scene, stunt performer James Winburn for the balcony fall, and, per the AFI Catalog, other cast and crew including Debra Hill wore it in specific shots.
What people actually said
“I put on the Michael Myers mask a number of times.”