That is true, but this happens even to credentialed users who speak on papers outside of their supposed field of expertise, even when their comment is within their area of expertise. If a mathematician points out a math error in a biology or climate science paper, it gets deleted. The mathematician rightly should know more about math than a biologist or a climate scientist, and the comment is still taken down.

Also, you shouldn't need credentials to demonstrate that you know something - the fact that you post something polite and useful should be enough to have your comment not be removed. It is a useful proxy for moderation at scale, though.

> you shouldn't need credentials to demonstrate that you know something - the fact that you post something polite and useful should be enough to have your comment not be removed

The moderators of the subreddit obviously disagree. From the sides I would say it works for them.

It certainly works for the moderators - I agree. Whether it works for the community is another question.