“Rewriting halachah doesn’t always need to be allowing things which were forbidden. It can go the opposite way as well.”
MW13: “True, but that only applies to passing off a new chumra as halacha. And while that does happen, these things usually understood to be a chumra/minhag/hanhagah tova, wich is not only not problematic but actually admirable. There is no issur against an individual or a community doing anything that is not absolutely mandated by Halacha.”
Maskim.