It would stand to reason that the number of comment votes would've dropped by some degree. Comment voting wasn't a big thing for a year because the BTC capitulation event in November 2018 caused the Steem price to crash, too. That's when the dust threshold hit and a lot of people, including myself, stopped upvoting as many comments as I had done so far. But yes, a drop in comment voting after HF 21 would make sense.