Is mocking some rulings of the jurisprudential schools of thought—such as the Hanafi school's prohibition of shrimp—considered ridicule of the religion, and is repentance obligatory for the one who does that?

Joking that involves mocking an established jurisprudential ruling is not considered mockery of the religion itself, unless the mocker believes that this ruling was brought by the religion. However, if he does not believe it to be part of the religion, then it is a mockery of a respected jurisprudential school of thought, which is legally and morally forbidden, and unbecoming of a Muslim, due to Allah's saying: (O you who have believed, let not a people ridicule [another] people; perhaps they may be better than them) (Al-Hujurat/11). Jurisprudential schools of thought are based on legal evidence. An example of this is Al-Kasani's objection to the impermissibility of sea animals other than fish, emphasizing that jurists argue with evidence, not whims. It is incumbent upon a Muslim to guard his tongue and not mock Muslims or their scholars.