Do critical comments make online articles seem less credible?
Yes, they bias readers' evaluations.
Negative comments are hard to ignore. Even when they're mixed in with positive comments, they cause readers to view online articles as less credible.
That could be a good thing if readers only reacted to thoughtful critiques; after all, comment sections are meant to be deliberative forums. Unfortunately, that's not the case.
Critical comments hurt content credibility whether they're civil or uncivil, and especially when they're authentic or vivid. It doesn't matter whether they include reasoned evidence. For instance, readers trusted an article on fracking less when it was followed by comments like, "Overreact much dumbass??? We've been fracking for decades — this just gives us more control over our energy sources!" and "Wake up idiots!!! It's too risky!!! How many times have we been told something's safe when it's not????"
There are a couple ways to counteract the bias.
When sites indicate that comments are moderated, negative comments have a smaller impact on readers' perceptions of credibility. Likewise, when other users respond to negative comments with conflicting views it mutes the first comment's effect.