I am absolutely 
ing tag synonyms and this new UI for managing them - nice job!
I think the surprise Sam is referring to that I also am feeling is that this is a blunt tool that has the potential to affect many topics. It’s certainly a Good Thing™ and a vast improvement, but because it can’t be reversed (there is no undo, right?) it might cause people to accidentally make changes they later regret, without realizing it. It may be overkill, but having a prompt to warn about the extent of the change that’s about to happen would help.