Etiquette on Down Voting

Interested in peoples views on downvoting. For example I just received a downvote on LinkedListCycle Two Solutions Fully Explained- 3ms -> 0ms.
I would never downvote without providing feedback on why I was downvoting. In this case I don't know what is wrong with the post or why it was downvoted and so I am unable to learn from what I have done wrong.
What do other people think, when downvoting solutions should we expect to have an explanation as to why the downvote?
Is there an accepted etiquette for this?

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