information:filtering, linguistic:voice_change
Comment system

Most videos enable users to leave comments, which have attracted attention for the negative aspects of their form and content. In 2006, Time praised Web 2.0 for enabling "community and collaboration on a scale never seen before", and added that YouTube "harnesses the stupidity of crowds as well as its wisdom. Some of the comments on YouTube make you weep for the future of humanity just for the spelling alone, never mind the obscenity and the naked hatred". The Guardian in 2009 described users' comments on YouTube as:

Juvenile, aggressive, misspelt, sexist, homophobic, swinging from raging at the contents of a video to providing a pointlessly detailed description followed by a LOL, YouTube comments are a hotbed of infantile debate and unashamed ignorance—with the occasional burst of wit shining through.

The Daily Telegraph commented in September 2008, that YouTube was "notorious" for "some of the most confrontational and ill-formed comment exchanges on the internet", and reported on YouTube Comment Snob, "a new piece of software that blocks rude and illiterate posts". The Huffington Post noted in April 2012 that finding comments on YouTube that appear " offensive, stupid and crass" to the "vast majority" of the people is hardly difficult.

Google subsequently implemented a comment system oriented on Google+ on November 6, 2013, that required all YouTube users to use a Google+ account to comment on videos. The stated motivation for the change was giving creators more power to moderate and block comments, thereby addressing frequent criticisms of their quality and tone. The new system restored the ability to include URLs in comments, which had previously been removed due to problems with abuse. In response, YouTube co-founder Jawed Karim posted the question "why the fuck do I need a google+ account to comment on a video?" on his YouTube channel to express his negative opinion of the change. The official YouTube announcement received 20,097 "thumbs down" votes and generated more than 32,000 comments in two days. Writing in the Newsday blog Silicon Island, Chase Melvin noted that "Google+ is nowhere near as popular a social media network like Facebook, but it's essentially being forced upon millions of YouTube users who don't want to lose their ability to comment on videos" and added that "Discussion forums across the Internet are already bursting with the outcry against the new comment system". In the same article Melvin goes on to say:

Perhaps user complaints are justified, but the idea of revamping the old system isn't so bad.Think of the crude, misogynistic and racially-charged mudslinging that has transpired over the last eight years on YouTube without any discernible moderation. Isn't any attempt to curb unidentified libelers worth a shot? The system is far from perfect, but Google should be lauded for trying to alleviate some of the damage caused by irate YouTubers hiding behind animosity and anonymity.

Later, on July 27, 2015, Google announced in a blog post that it would be removing the requirement to sign up to a Google+ account to post comments to YouTube. On November 3, 2016, YouTube announced a trial scheme which allows the creators of videos to decide whether to approve, hide or report the comments posted on videos based on an algorithm that detects potentially offensive comments. Creators may also choose to keep or delete comments with links or hashtags to combat spam. They can also allow other users to moderate their comments.

In December 2020, it was reported that YouTube would launch a new feature that will warn users who post a comment that "may be offensive to others."