I recently re-tagged a question with the grades tag. I then looked at the synonyms and there is the grading tag. I can't vote it as a synonym because my rep on either of these is probably 0. But there is a down-vote on the synonym suggestion, see:
https://academia.stackexchange.com/tags/grades/synonyms
What are the possible reasons for this? Isn't it the consensus to try to clean up these tags?