Are multiple solutions with the same nonce valid?

Are two different solutions with the same nonce, from the same worker, considered valid or do this represents a duplicate share?

Since there exists more than one solution per nonce, that shouldn’t be the case, or am I mistaken?

Equihash generates on average somerwhere around 1.8 solutions per nonce (sometimes as many as five or six). Each of these solutions can be tested for satisfying the difficulty. So yes, if multiple Equihash solutions, when combined with their nonce, satisfy the target block difficulty set by a mining pool, then they should all be considered valid shares. Incidentally, this is why Equihash is measured in solutions per second (Sol/s), not hashes per second.