Regardless of if you knew who the payment was coming from at the time, or what the purpose of the payment was, the transaction did in fact come from TF.
The blockchain trail leads to 2013 to an address potentially connected to TF (Inputs.io hack), but that's not conclusive or the evidence was presented somewhere yet to be seen by me. The story regarding the situation is certainly unusual.
What you decide to do with it is up to you, and should depend among other things, if you have provided actual services prior to this post in exchange for the payment.
The real idea behind the payment is to fund a lawsuit against a certain individual. I also plan on PGP signing this.