yeah you can't distinguish between bots and humans. But like said in the post, currently the top100 commenting subs only take part in ~10% of the total comments. This would fit with the dead internet theory imo.
But it is also important to note that for this info the comments/day numbers come from two different sources, so it is hard to verify the validity.
The comment numbers of the top100 subreddits are from subredditstats.com, while the total is from the script used by blackout.photon-reddit.com
For subredditstats.com there is no way to see how the data is obtained/tracked.
But the blackout.photon site has its source code available. I just have not enough programming experience to tell if the comments/min number is obtained by a direct api call, or if it calculates the comment ID Delta between each call that it does (it calls the most recent comment each minute).
Nice, i just wonder how many people have 2-3 accounts to test out different communities