You gave us an out of context comment. The comment says that not purchasing the chocolate does not change the fact that a child laborers for it. The comment also states that, for the sake of argument, the theoretical consumer in question doesn't have access to ethically sources chocolate. The comment comes to the conclusion that choosing not to buy has no material effect on the victims. And it is correct.
You seem to think that this means they are trying to absolve someone of their responsibility. I disagree with you. You also seem to think that purchasing the chocolate breaks solidarity with the victims. I disagree with you.
First off, the company that sells the chocolate is the retailer. They have already purchased the chocolate candy from the chocolate candy distributor. The chocolate candy distributor may or may not have already paid the chocolate candy producer. The chocolate candy producer has definitely already paid the cocoa distributor. The cocoa distributor has already paid the cocoa producer. A person buying chocolate from a corner store has not actually given any of their money to the company engaged in child labor. The money that goes to the company engaged in child labor is spent months before the choice of the individual is made, and the amount of money is based on large-scale global aggregate trends, not based on the individual morality of consumers. If we have a moral responsibility, it's to raise awareness of the practices, which companies are engaged in it, and, if you're not going to engage in revolutionary liberation, then at least pursue reforms that can actually have an impact on the practice instead of saying "I have met my moral responsibility through self-denial."
As for breaking solidarity with the child laborer, I question how you think that happens. The child laborer has no idea which chocolate candy products contain their labor. The child laborer has no relationship with the chocolate candy consumers. There is no means by which solidarity can even be formed here such that it could be broken by the act of purchasing a chocolate candy, unless you are positing some psychic karmic cosmic framework of morality. This is partly why visibility is critical. Activists who seek to raise consciousness on these topics often use photos or videos of actual children and then associate them with specific brands and trademarks in an attempt to create the conditions for solidarity to begin.
The problem is that you (and other commenters here) are inverting the base and superstructure. You don't free the workers through convincing people of the morality of it, you convince the people of the morality of it by freeing the workers. Ideas are determined by our material conditions. Yes, ideas then influence our material conditions, but they do not determine it. We must actually change the material conditions to change the way people think fundamentally, and the evidence is against the idea that private consumer boycotts can be that material change.