But this does suggest that it would be different to comment on a board like this. People wouldn’t just be making comments for the joy of discussion, they would be making comments with their hands out for a tip.
I think this incentivizes low investment drive-by comments, but perhaps this could be fixed as well. For example, you don’t have to display the actual upvotes/downvotes score of a comment, you can display and sort by a score which is a function of those things and additional information about the quality of that comment, incentivizing comments which are both popular and insightful.
The key factor is that people who have a sense of belonging or ownership will donate their time and expertise. People on /r/AskHistorians go to extreme lengths to provide ultra-high-quality answers for free because that's what it takes to be part of that community. The one time I felt like I actually had something to contribute I started my comment (a reply to another comment, there's zero chance I'll ever be qualified to provide a top-level response) with "It's an amazing day, I actually have something to contribute here!" And many people start their comments that way.
A paid environment -- especially one where the compensation is likely to be trivially small -- is far less likely to engender that sort of participation and support.