Novelty/troll accounts. I've seen a lot of them pop up on Reddit over the years. The most infamous one I remember was one called Gradual_****** (yes, the n-word) that would type out ordinary replies that would gradually switch to ebonics.
I recall that from many years ago. Some of the wayward white American culture on that site is definitely off putting. That user was generally received well which says a lot about the soul of a community (or if it even has one).