I dislike this idea because it creates "tiers" of users. Communities might not allow comments from anyone without at least the basic donation badge. Donations incentivized with perceived perks are made with selfish intent. The capitalist system has trained us that in order for people to do something, they must be given a sufficient reward.
This is not true. Using rewards as incentives to motivate people will create division among individuals. When rewards are introduced, the focus shifts from intrinsic motivation and personal satisfaction to the external reward itself. This leads to a competitive mindset where individuals start comparing themselves to others solely based on the rewards they receive.
For example, I've seen something as simple as a user tag being used to restrict and divide a community. (r/conservative comes to mind first).