Support. Also wouldn't mind if the tag was called Ultra rare or something like that. And make it a pinkish purple with OMGSR being a dead purple.
The rarity tag does help the rare's list out, especially if it goes to a "Rarity" format like suggested. This helps a lot of problems in the trading community and is more beneficial than detrimental. I don't understand the "It will effect common" pet's argument though.