...
...
i believe there is a way to know that the process you mentioned can be identified as "mixing" by blockchain analysis..therefore it can be safely assumed that John received coins from mixing..
Bob's original coins were spread among participants of the mixing..therefore it can also be known how many of Bob original coins were obfuscated/lost to mixing (were split/participated in the mixing).
...
Yes, it's probably possible. So what? Mixing coins is not illegal by itself. It is still impossible to know and to prove that it was Bob who sent coins to John. That is why you should mix coins in advance and better not the exact amount you are going to spend privately.
Coinfirm will not be able to deanonymize transactions. Nobody was able to still.