Thanks for the suggestion. I created an MR to add a slightly edited version to the "Best Practices" section of the page: https://gitlab.com/gitlab-com/www-gitlab-com/-/merge_request...
This is an incorrect view of HN. The last bit is true, but it's fine on HN to upvote or downvote based on whether you agree with it personally. This was established by pg himself many years ago.
I don't think that controlling your employees' upvote or downvote rights is a good idea. You may want to add an advisory that downvoting a comment about GitLab could be unproductive, but anything beyond that feels micromanage-y.