Unswitched hot in Fixture Junction Box
Clarification: I think that there was a miscommunication in the post that you are referencing. It would be illegal for a neutral wire to be shut off (disengaging a light or device by breaking the neutral conductor). brhans didn't mean the fixture was hot (breaking neutral). brhans was saying the hot passes through the BOX and goes to the switch, and CarlWitthoft was confused, saying that a hot wire connected to the fixture would be illegal (meaning the switch was breaking neutral).

It is legal for (hot) wires to pass through a junction box. NEC Chart 314.16.A says how many wires (sizes) are allowed in various (sized) boxes.