There's a reason Wikipedia isn't an acceptable source in college-level courses.
Congress was looking at evidence of what that particular user was doing online at the time, because /u/stonetear posted questions that look rather incriminating in retrospect based on what we've learned since then.
This kind of thing is why it's important to establish a chain of custody for evidence.
There's a lot we don't know without knowing the internal workings of Reddit, though I agree that you can't have to think that if one rogue person (even someone like that) can just do such things, they don't have robust internal controls at all.