Some like toning, some don't.
In this case, heavy patination has destroyed all of the cartwheel mint lustre.
Nevertheless, cleaning the toning off will reduce the value.
I would not take the risk to remove the patination.
Patination such as this can help preserve the metal underneath. This is one of the reasons why ancient coins (especially bronze and copper), have survived as long as they have.
With patination, some of the surface metal has been converted into metal sulfides or oxides, or a combination of both. To remove the patination is to remove some of the converted surface metal.
Patination is, after all, a form of corrosion.
For those of us who wish to preserve cartwheel lustre, put the coin in an acrylic screw capsule, or have it slabbed.
We all get old, so do coins. Coins are a bit more durable than us.
