Pretty interesting, thanks! Comparing it to the data from 2017 [1] it looks like a ~30% increase in the number of comments (from 900 million to 1.2 billion), while unfortunately the number of votes/upvotes provided for the two periods is not consistent: they mentioned 12 billion upvotes for 2017 and 27 billion votes (which presumably included downvotes) for 2018. All in all not bad, let's see what 2019 will bring to them.
[1] https://redditblog.com/2017/12/19/the-best-of-reddit-in-2017...