Bran watched them come from a guard turret atop the outer wall, peering through Maester Luwin’s bronze far-eye while perched on Hodor’s shoulders.
Is there perched the participle or the past simple? Why the subject (Bran) of the action (perched) is absent in the while-clause? I know that while can be used without a subject with ing-form of verbs, but there is ed-form, no ing-form. Shouldn't we rather correct the sentence in the following way
Bran watched them come from a guard turret atop the outer wall, peering through Maester Luwin’s bronze far-eye while he perched on Hodor’s shoulders.
or
Bran watched them come from a guard turret atop the outer wall, peering through Maester Luwin’s bronze far-eye while perching/sitting on Hodor’s shoulders.