I recently got the taxonomist badge awarded for acs.
However, I am sure that I do not have used this tag. I did not even know what it stands for.
Is there a bug?
There's a deleted question here: Sphere rotation problem - points jump before turning that you added the tag to in the most recent edit, the badge is behaving correctly...you created the acs tag, you just can't see the question you did so on anymore...until 10k!