In direct answer to your question; no. I might make life miserable for the thief, but what's done is done. I have neither the resources, time, nor the inclination to be bothered with pursuit of my copyrights on the consumer level.

I might, however, feel a bit differently if I had made the initial investment of purchasing expensive tools, hiring models, paying for studio time, added to the hours of labor involved in creating a photorealistic character, and seeing other people making a profit from my hard work while I receive no compensation.
While I may not agree with Stefania's stance, I certainly understand her frustration. If I were to purchase a texture and find out that it was pirated (as has happened to me just last week in a trade), I would, and did, approach the original artists and offer to work something out.
I certainly do not agree with your attempt to blackmail the merchants of this site into agreeing with you by threatening them with your "No Buy" list.
Go ahead and put me on it if you want.

Realistically, I know that it would be a complete waste of energy to pursue the matter on the consumer end.

That's really not my point here. My point has to do with the seemingly double standards of many members of this community and the administration of this site.

They seem to have no trouble pouncing on, or banning anyone who they think might be talking about warez, without a thought given toward education and forgiveness of a first offence (zero tolerance). Yet merchants who sell pirated and unauthorized derivative works are allowed to continue indefinitely. The product in question might be pulled, but there is no other apparent consequence. It is completely up to the original artist to pursue costly legal action...usually futile as well. Adding insult to injury, known thieves are not only allowed to remain members of this community, but also to continue doing business here.

To top it all off, merchants who have the audacity to inform the public about someone stealing from them are made out to be the villians. If an honest mistake is made, and the parties involved can work something out (which they should be given the chance to do,IMO), that's good; but there still need to be consequences to discourage this type of fraudulent activity.

I can easily forgive a mistake. What I cannot tolerate is deliberate dishonesty or hypocracy.