Does anyone think they can reject an offer that is above the current share price without making the rejected offer public? I know they said they would reject an offer they thought was too low and go into negotiations, but if an offer exceeds the current share price, isn't that material enough that they have to make it public? Opinions?

Unfortunately, imo, I don't think they can make it public as any rejected offer would still be under a non disclosure agreement just as any negotiations are part of NDAs. A rejected offer doesn't mean a final offer as the party (Teck) could come back at a later date to make a new one. So if Teck doesn't want anyone to know they are pursuing the acquisition of Cuu surely they would also not want anyone to know what offers were rejected as well.