It looks like Facebook is rolling out the new upvote and downvote feature on local FB groups, as reported by eagle-eyed users recently. The upvote and downvote buttons that reside next to the Like button on your FB group is similar to the one on sites like Reddit or Facebook, which allows community members to rate a particular comment depending on its usefulness and value.
Rating a comment happens anonymously and is the closest thing that Facebook has to a dislike button, at least for now. This particular system is useful for filtering controversial or useless comments, but like any other crowdsourced feature, is prone to abuse via brigading and other means.
As of the moment, Facebook follows its existing algorithm for sorting comments to display “most relevant” ones regardless of it actually being actually useful. It is not clear if reactions also contribute to making a comment more visible.
Facebook community admins are often overwhelmed by the number of user reports they have to attend to but with this feature, the site can automatically bump upvoted comments to appear higher in a post with the help of its users’ rating. This especially makes sense to see in Groups to encourage engagement and weed out spam comments.
The upvote and downvote Facebook feature had its first round of limited testing in 2018. There was speculation on whether this feature would influence the outcome of the US elections that made Facebook decide against completely rolling it out. It was revived again in November of 2020 with its latest iteration asking you to classify upvoted comments as helpful, new idea, kind, education, entertaining, or relevant.