>my question is about the ease with which someone can identify the common ancestor from before the tx0 if 2 or more of the 5 outputs from the tx0 are later recombined.

Easily, and in some cases, with certainty. The structure of Whirlpool makes this worse, but it's an underlying problem for any private currency system: Some people have realllllly short time preferences that undermine their anonymity.

Kruw

my question is about the ease with which someone can identify the common ancestor from before the tx0 if 2 or more of the 5 outputs from the tx0 are later recombined.

for instance if I had a single kyc'd utxo which tx0 split into 5 equal utxos and then those go through many rounds of whirlpool mixing, does combining any number of them trivially link them back to the original kyc'd input (since it is the obvious origin of all five)?

AskSN

Coinjoins

Risks of recombining utxos from Samourai mixes

wackster

I'm willing to accept all of this.

my question is about the ease with which someone can identify the common ancestor from before the tx0 if 2 or more of the 5 outputs from the tx0 are later recombined. 

for instance if I had a single kyc'd utxo which tx0 split into 5 equal utxos and then those go through many rounds of whirlpool mixing, does combining any number of them trivially link them back to the original kyc'd input (since it is the obvious origin of all five)?