“To determine damages the courts will determine whether the certifying agencies reputation (business) was damaged by negative remarks.”
There are no damages awarded if the negative remarks were true. And the court will refuse to determine whether they were true for the earlier mentioned reasons.
“Don’t take my word for it, look up the case law”
I already cited case law above supporting what I am telling you. You will not be able to find a case by a kashrus agency successfully winning a lawsuit against someone for saying their kashrus certification is unreliable or non-kosher.
“You can definitely say this persons qualifications do not meet my standards, but you can not say “the food that person certifies is not kosher”.
You can say that Kashruth Agency Z certifies non-kosher food as kosher. Or you can say Kashruth Agency Z’s certification is completely unreliable.
“The more private an individual the better chance they have at a successful defamation suit.”
Regardless whether they are private or not they have little to no chance of being successful in a defamation suit based on someone stating the food they certify as kosher is treif.