I sent back 32.51 and 50.00.
I badly wanted to find some way to include a comment with indirect transfers, but there just wasn’t a way to do it. Bitcoin uses EC-DSA, which was essential for making the block chain compact enough to be practical with today’s technology because its signatures are an order of magnitude smaller than RSA. But EC-DSA can’t encrypt messages like RSA, it can only be used to verify signatures.