Oh, you can eat Esbit. It is a hexamine tablet with a slightly different binder than military hexies used, hence the slightly smoother texture. Hexamine is also has, or at least had, certain veterinary medicine applications.

That being said, it was for larger meat animals, and in teeny tiny doses so that the CNS and kidney damage wouldn't have any long term effects that wouldn't make it past the slaughter house. For a human, eating an esbit tablet would be a couple thousand times the dose given to say, veal calves. Among other things, the break down on heximine produces formaldehyde- that's why they say neither you nor your food should come into direct contact with the fumes. I think it would be a race to see which stopped working first- your nervous system, your kidneys or your liver...

Oh, and I don't think he was saying he ate one. I think he was coming up with a theoretical moron.