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Downvoting on Hacker News literally silences the posters. Not only are their comments hidden, they can't post more comments for some time (say in response to what people are replying to them).

Downvotes are supposed to be a tool for filtering out spam, off-topic comments, links to malware and scams. They're used to cancel people for having an opinion that differs from the group.

In this case apparently the group disagrees what the function of melanin is.