I'm a firm believer that a tortoise should have nice fresh food just like me and my children. I would say no to tofu because let's face it..... That's not real food hahahahaha I won't eat it so how can I feed it to my baby?
That's a good question though, never really thought about it.
I would agree with not feeding it. Legume seeds are usually not a good choice and as a protein substitute, animal protein is to provide amino acids that don't exist in plants, as well as, D3 - neither of which would be gained from tofu.
The question comes down to what is in it, seems like a pretty exspensive food source either way.
wiki says it is made from bean curd, and soy milk, yecch, I would avoid for tortoises, and people.