If they were on the same block, xnode would not have lost its coins in case of orphaned block, right? In other words, they both went to wrong fork and once it is detected it could be corrected.
Another question is how to ensure they are on the same block.
Current design require two tx.
Make it to single tx.
Why two txs cannot reside in one block?
A ---- mixer ---- B
tx1 tx2
There is network delay.
Actually A is broadcasting to network his tx, signed by his private key.
A commuinate mixer to know which address should be used, mixer issue a address for A, and inform mixer real payee.
It should be included in a block.
There is possible way, if mixer relay the tx solely.
Hold the tx1 and process tx2, broadcast tx1 and tx2 simultaneously.
But who generate block ?
There is network delay.
tx1 and tx2 can be splitted to two blocks sometimes. no 100%.
By any means decribed in
https://bitcointalk.org/index.php?topic=631052.msg7289855#msg7289855