My situation is the same as Vargr's. I use a "Source" tag which I create 2 of in every topic. My main realm is sitting at over 2800 topics. I totally understand why LWD made the change and I agree with it. The joys of being an early adopter.
Short term pain for the long term gain.
Source is a reserved name so I've renamed one to Reference. Since one of my sources was always the publisher, I renamed that to Publisher. However, some publishers are under Reference and some references are under Publisher because they had both been called Source originally without any differentiation.... So I'm doing a topic-by-topic check while also removing other snippets that are now part of the official structure that I'd added. Might as well clean it all up at once.