By special permit, the Board of Appeals may permit a nonconforming use to be substituted by another use, provided that the substituted use is permitted in the same districts in which the prior nonconforming use is permitted, and provided that the new use will be less objectionable in terms of noise, traffic, or other characteristics than the prior use, except as specified in Section 8.02. Uses not allowed in the Harvard Street Main Street Corridor districts (H-MS, H-MS-O, H-MST, H-MSN) may not be substituted for other uses not allowed in those districts.