>>/809/
Tag siblings and parents are now virtual at all times. Unfortunately, it was too technically complicated to maintain a system that could do both soft and hard replace, and it was too difficult for the PTR janitors to manage clients who could hard-spam variously incorrect tags based on personal sibling relationships. The PTR problem would have only become worse as I added the ability to apply different services' siblings to each other.
So, for now, the ability to hard-replace tags with their preferred siblings is gone. Tags show more reliably as their sibling ideals in normal displays, but they aren't stored that way. The nice thing about this is that siblings (and parents) are now completely undoable in the case of mistakes.
I expect to add in a different system for hard-renaming and so on, for local tag services, in the future. It will be a different system than siblings, probably called 'alias' or similar, as some boorus do.