Self-voting is allowed on Reddit. In fact, your posts there are upvoted by default.

Being able to self-vote is not what makes Steem distinct and it is certainly not a merit of the platform.

On the contrary, I believe it retards the rate of adoption by people who understands the natural bias of self and how that affects actual quality and the level of effort authors put into their work. Self voting lends to complacency (especially higher stake holders ) don't necessarily have to work as hard whereas a minnow busting their ass creating content is under rewarded. This is centralization and has the tendency to result in less diversity of content.

I have seen a ton of low effort content receive inordinate rewards because of rampant self-voting and vote-buying. Because of this and other problems, I agree with this initiative of @l0ki and @personz 100% although I am not sure of it's current state.

To be frank, it is the nature of the self voter to oppose this because it undermines the very mechanism by which they are profiting in a manner that MANY believe is ethically questionable. They are making relatively easier money which is precisely why they don't want to level the playing field. Well, the end result is Steem is "pay to play" not unlike politics. I will say it and will say it again. Self voting is antithetical to decentralization and is why I have been apprehensive about investing any more money onto this platform and I would venture there are not only a few of us that feel the same. We are many but are voices muzzled while the voices of self voters get louder.