Buttons added to comments and posts that allow members in a forum to vote content "down" in a discussion thread

By pushing down certain types of comments or posts, members can signal and reduce low quality content for others and send a critical signal to the creator of the comment or post.

Papakyriakopoulos et al. (2023) examined nine subReddits that removed their up & down vote functionality to see how those changes affected the quality of discourse along the three dimensions of civic, deliberative and demagogic discourse. The researchers constructed a quasi-experiment by matching those subReddits with other similar ones that did not remove up & down votes (which Reddit includes as a default setting); by comparing any change in discourse quality to the "matched" subReddit they were able to distill the impact of the switch in functionality (researchers call this a "difference in difference" design). They found that when a subReddit removed down votes, keeping up votes, there was an improvement in discourse across all three dimensions; civic and deliberative discourse increased while demagogic discourse decreased.  (Note: all effects we include are statistically significant, unless otherwise stated.)

A separate pilot field experiment conducted on r/Politics (Matias, 2018) found no effects of removing down votes, yet the author notes the study was underpowered, i.e. they had too little data to be able to see a statistically significant effect.

Overall, evidence points to the likelihood that including downvote functionality may degrade discourse. Because Papakyriakopoulos et al. (2023) is a quasi-experiment, however, we cannot rule out that some other confounding variables produced the effects we see, so more evidence is needed (ideally a field experiment on another platform) to confirm the negative effects of allowing downvotes.

Note: While downvotes may have a negative impact on online discussions, up votes are likely to have a positive impact.