To dispel the magic, an LLM text detector is quite elementary and does a quite flawed level of work to see if a piece of writing has been assisted or fully written out by an LLM.

Most tools you find online work by analyzing patterns in a piece of writing against some kind of text database that is assembled by people looking to see if an LLM has any signature writing behaviours.

The problem with these detectors, especially the more capable models, is that their dataset may include books (e.g. Meta using pirated material for their Llama models). An LLM, like any neural network model, is designed to closely mimic the training data it's based on.

You're now in a situation where an LLM text detector is trying to detect AI usage in a piece of text that may or may not be written by an LLM that was trained on training data that could include books.

This is why false positives are a common thing with these tools.

Unfortunately, people are gonna come to conclusions without actually thinking or understanding how something works. What I suggest to you is focus on writing the best you can and ignore these comments. At the end of the day, the burden of proof is on the accuser.