Yeah, though that was hardly the worst of it. He himself was personally involved in horrific abuse of the natives -- so much so that the Spanish imprisoned him over it.

Lots of other people realized what Columbus had found, even though he never did. He was wrong about the size of the earth, and everybody knew it. So he managed to find something he had no reason to expect, and didn't understand it. Others did.

If a tree falls in the forest, does it make a sound? If someone discovers something and nothing really comes of it, is it really a more significant discovery than one which changes the world profoundly, immediately, and forevermore?

When I was a kid I remember seeing weird bugs in the garden and wondering if I was the first person to find that bug. I’m sure I wasn’t, but in theory I could have “discovered” loads of new species - but would it even matter if I wasn’t aware enough of my own discovery to share it?

Did the Vikings even realise they were on a new continent? My understanding is that they “settled” a tiny area and may have thought it was just an island off of Greenland or something.

I would say yes, "making noise about it" would be a relatively important part of discovery. Did Erikson know that there was an entire continent with advanced societies completely seperated from the "old world"? Because that is what Columbus discovered. I'm making the distinction between Leif Erikson discovering a tundra-like landmass beyond Greenland that they didn't think was significant, and Columbus's actions which ended up connecting the old world to the new. Those two things are very different from each other. If I google "who discovered america" and got Leif Erikson, I think that would be more confusing than Columbus.

well yeah Erikson was first, but he didn't "discover" it in the sense that Columbus did. I would say they're categorically different. See my comment below.