I've vouched several green user comments in the past six hours that had been flagged and gone to dead for no apparent reason, the GP comment you spoke for was one that others had kicked to dead ( usually I'm flagging obvious spam comments straight to dead ).
https://news.ycombinator.com/newsguidelines.html
Comments like this are particularly bad because often, as in this case, people post corrective upvotes and then the now-inaccurate complaint lingers on like uncollected garbage.
https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...
You're right, of course, that a legit comment from a new user shouldn't be downvoted, but it's enough to make a corrective upvote yourself and move on; or, in egregious cases, let us know at hn@ycombinator.com so we can fix it.
(We detached this subthread from https://news.ycombinator.com/item?id=43778319.)