An r-block b with an empty payment and comment (disapprove, h′) pointsto an r-coin payment block b′, where h′ points to the reason for disapproval: To b′, if it isunbalanced, or to a block b′′ equivocating with b′
Again, this can be derived out of DAG. Seems redundant.
It would somewhat spare computation, as one can check equivocation by following a pointer, but then he would need to ensure that both equivocated blocks are observed by a self-parent chain of the "DISAPPROVE" issuer.