Signature means, "what we expect to see." Trademark would mean, "he was the first or is the only."
I agree. Silva has no "signature" move(s). He's probably the guy with the least repetition of how to end his fights and what kind of technique to use during the fight. The only constant is that he comes up with something new.
The article above is not about Silva's signature moves, but a glimpse of his arsenal of techniques he is able to apply in a fight.