Comment by chefandy

This is fundamentally a support and UX problem, not a dev failure. Big production user management and authentication systems can get pretty complicated and trying to figure out every weird edge case when combining them is not low-effort by any measure. "What if someone's username wasn't caught in their profanity filter but gets caught by ours" seems like a pretty rare edge case in a huge pool of big problems to solve. Their shortcoming was not giving their users proper guidance on how to address the inevitable kinks that pop up.