I came across the globaltag-megablender tag while handling a lost user.
Now, the tag seems to be about a specific thing. It just doesn't seem clear what that is. It's oddly consistent over how its used, but I have no idea what feature it is.
It lacks a tag wiki to boot.
It is mentioned in The Many Memes of Meta, but it doesn't feel like the Stack Exchange™ MultiCollider SuperDropdown™
So what is (or was) the GlobalTag MegaBlender™?