The incentive is there just as much as the regular posts in terms of the reward pool. The problem is that most of the users aren't really users, they are bots or trail followers. This doesn't change anything for the actual people who can do the engaging. They aren't even engaging now. Upvoting as autovotes or trails isn't engaging. You're own individual consciousness needs to get involved if you want to be engaged in something. If people do it change their bots and upvote and trails to add comments, nothing will change for real engagement. It's just more reward incentives that mask the real issue, and don't deal with the real problem: consciousness of individuals and their behavior. Actually get people to engage in posts, and therefore comments, and then you will get more real engagement. Setting another rich target niche through another reward pool mechanism for bots to exploit is not a solution.