Maybe I'm missing something here, but ISTM the question isn't really whether the logs are of a genuine conversation about CP, but rather whether the accused really was a part of that conversation? After all, if he really took part in a conversation about procuring such material, it wouldn't have mattered if he talked like a newb. Likewise, if he wasn't in on it, it doesn't matter that everyone who was in on it got "the lingo" right.
ps. How would one know enough about the scene to motivate such skepticism?
Send an undercover agent to immerse himself in the community, learn the lingo, etc, and use opsec to protect him from detection by external authorities (the same authorities that failed to bus everyone else in the community already). Then when you want to disappear someone, create some links between the real person and the online persona created by the undercover agent.
I’ve been on IRC for decades, a few years running a file distribution for audiobooks, which sadly meant I ran across some things I’ll never unsee. I’ve never seen anyone actually say “kiddie porn” who was actually looking for or offering it. It’s all “loli” or filename references, and “#yo” stuff. Those chat logs sound ridiculous, but I have to admit that my experience is limited to channels where cp wasn’t welcome. Maybe when they’re on their own they start talking like a special agent?
To me, it would be like being in a warez channel full of people saying, “I want pirated material.” That at least I have experience with, and someone saying “Where the copyright violations at?” Rather than “any good ftp’s and xdcc’s?” Would raises red flags.
Wow you really misrepresented those chat logs. The personas portrayed within appear to be interested in the concept of CP, seemingly mostly for its forbidden nature. Whenever they discuss an individual file, there are questions about whether the participants are 15yo or older, or whether the file is "really porn". If these are really the deepest depths plumbed by that "scene", the whole thing has been wildly misrepresented.
ps. How would one know enough about the scene to motivate such skepticism?