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This is a design feature of all Boeing 747, which have ventilation ducts routed from the engines to the ceiling through this area. Therefore, 3 windows are missing just before the 3rd door, the #3,5 and 7 going forward from the 3rd door.

As a result, the last 3 or 4 rows in the forward economy class section (except the last one, row 37 on MH) in a typical layout have one out of two windows missing. Depending on seatback angle, you would indeed be facing a wall in 34A.

On the other hand, I find this first economy class section often quieter, as groups and such are often seated further back.

Also, the outboard middle seats and 'E' seats on MH 744 Y class have limited legroom due to the box housing PTV electronics. Avoid those!