Personally, I do not imagine that these guys failed to hide their identities, although their history proves how smart they are. The name of the suspect that was announced may have been used as his identity only and has nothing to do with the matter. I am not going to open an investigation here, and all I want to say is that things are open to many scenarios as long as Chipmixer keeps data on servers like any centralized website.
Reportedly they tracked Nguyen through a transaction on his paypal account and there was mention of chipmixer there.
I do not understand exactly what this document is? The internet address says "press release". So this is just a general document for the press? Or documentation of all the evidence and procedure from the special agent?
In any case our forum are very common there. The word Bitcointalk ist 14 times represented.
and on page 22 is the first-word "bitcointalk" forum written.