Tell me, is HummerX and Sinkillr the same person, or different people? What does your analysis of style tell you?
To be honest, I could care less whether they were the same or not.
I would trust neither as a reliable source of information. So you say people can make up stuff, yes? Or that it is hard to figure out multiple accounts? For the sake of argument, let's say that you are right. It is impossible to determine person A and person B.
The thing is, credibility takes time to build up. I don't believe anything anyone says to me without thinking about it carefully and who said it. If you were to make a new account and there was no way to know that it was you, that new account would have no posting history, no way of knowing who they are, what they have said in the past, or who they really were.
I would only take someone seriously if they are either someone I know or someone who has an established record within the community (and you can tell by their posting history).