It is speculation. They do not exist. You're thinking of Maltego, and it's very far from what is being described.
Palantir makes software, not a panopticon for their own use. High frequency trading is entirely unrelated to scrounging the deep dark web for crumbs to stitch together forum accounts.
This is a fantasy spurred on by too many dark mirror episodes, nobody does stuff like that for the hell of it. Storing the amount of data we're talking about is expensive. Collecting it is expensive. Processing it is expensive. There's little money to be made with it, but it sounds really good if you don't think too hard about it. It's illuminati conspiracy mumbo jumbo for nerds.