That was spam too, but there is a big difference.

The Reply Guy was easy to detect with 100% accuracy, through a hand-written filter.
Some used a less precise filter based on the string "reply guy", rather than the full content for the post, but a perfect filter was possible.
Even later bots, like the one that scrambled the post it was replying to, instead of copying it, were easy to detect algorithmically. I still have those filters active.

These new bots are not easy to detect programmatically.