I'd say at least 1/3 of internet commenters clearly have GAD (generalized anxiety disorder). Most of them undiagnosed. Anxiety triggers ancient animalistic parts of the brain and the "need to do something NOW" which often then gets released into negative / angry / aggressive posts.

Depressed people are the opposite, they tend to lurk and not care that much

I remember back in the "old" internet pre-2010, there was basically zero anxious people posting.