Maybe they are dogs! Maybe they are robot dogs! You Don't KNOW!
BTW it's less scary if you think most of these comments are written by morons. A "smart" bot comment (like an informative one) is still way better than a comment written by a human idiot.
These low effort and low quality comments used to be the norm when reddit was new. Eventually the community kinda wised up a bit and realized that you don't need a "when does the narwhal bacon?" comment chain in every thread and heavily downvoted this sort of thing. Then the reverse happened and reddit become known for housing the internet's most insufferable know-it-alls, contrarians, and pedants. I think it kinda still has that reputation a little bit, but maybe the metaphorical boomerang is swinging back around again? Either that, or like you said, bot infestation.