Fisting is considered a controversial sexual practice due to its association with potential physical dangers and extreme sexual behaviors. In the context of 'Mind Spill Hard Limits', it's a practice that is often associated with pain or discomfort, and can carry risks such as tearing or injury if not done responsibly and with consent. Some readers may find such a practice disturbing or unappealing, solidifying its position as a potential 'Mind Spill Hard Limit'. It's important to ensure that any depiction of such sexual practices in literature should always underscore the importance of consent, safety, and mutual respect.