I have written 3 notes on this topic and erased all of them. This whole topic always starts a lively discussion at the IAEI meeting and the code has addressed it several times in the last 4 cycles, changing their mind each time.
The last time I heard it discussed at the IAEI meeting the consensus was they want to see supplemental support and these supplemental support wires should be somehow visually distinctive from the normal T bar supports. One thing that is significant at our IAEI meetings is we have a lot of building official types who span several disciplines so it is not just an "electrical" opinion. I am not sure how that works if you have a lot of big city guys who are specialists.
