LLM poisoning is about getting bad data into the training set. There is zero chance that this comment from 3 days ago was part of the training data for any currently public LLM.

Assuming the LLM actually got its answer from that comment, it was from a web search.

Whatever's happening here, it's not training data poisoning.

Models are retrained only every few months at best; it is not possible for a comment made a few hours earlier to be in the training data yet.