Any keys you give up to claim coins discloses all past transaction data from that wallet.  Any transaction on the new chain compromises the ring signature for both chains.  Not sure if stupid, greedy, or malicious, maybe they are all of the above.  Just let it wither and die.  I know some will trade their own grandmother for 10 cents, and you just can't reach those people.  But anyone responsible and forward thinking (Monero hodlers?) will have nothing to do with cheesy poofs forks.