I'll quote another reply to me elsewhere in this thread.
It is annoying to see a reasonable comment downvoted to 0, or less. I feel like I'm missing something and what I'm missing is an explanation. Why was the comment voted down?
Now what happened in the grandparent of this comment here is that another HN participant asked why a particular comment of his in another thread was downvoted. I kindly followed the link he provided, to see his comment for the first time. After reading that comment, I pondered his informational question in this thread about why that comment was downvoted. I don't know FOR SURE, because I had no role in downvoting that comment, and indeed wouldn't downvote that comment if I came upon it in a thread I was following actively. But I suggest to him one reason why somebody--unknown to me--might have thought to downvote that comment. Then I see that my own informational answer to his question was downvoted--for reasons not stated in this thread. There is some kind of signal here, but I sure hope that the signal is not "Don't answer informational questions posted by other participants."
The answer I gave above was a hypothesis based on previous comments I have seen with downvotes. But the hypothesis doesn't fit the answer itself being downvoted, which for all I know was simply drive-by downvoting.