If it's not allowed, it raises the potential for people to sell their Steem because it's not worth as much to people who bought in under these conditions and understanding these mechanics. That would drive the price of Steem down substantially as there are a lot more people earning Steem than regularly buying Steem on Polo or Bittrex. On the margin, this could radically lower the price of Steem, which in turn would reduce the rewards for writing posts and curating for minnows and dolphins and curb their creation and activity, and so on.
That's why all these issues aren't simple -- there are tradeoffs in every direction and human beings grouped together are complex adaptive systems.
Like the sun in its' effect on the earth, the biggest controller of the value of Steem is purely the subjective opinions of the markets. Price going up and down will be not caused by something as simple as a HF with a ban on self voting, most likely. But outsiders are gonna think self voting is lame, this is everyone's first response before they start to think about it, and not be so sure.
Why is it you are forgetting that voting, posting, flagging, these are NOT market phenomena, as in money? These are culture exchange, this is the correct place for democracy. The objective of Steem's design is to facilitate the reward of the production of items of culture that are most appreciated by the users. Self voting does not provide that information to the network.
And as I have mentioned elsewhere, the incentive for people with strange ideas about valid ways to earn money? They will come and spam it up so they can pin their self votes on it.
We will see soon enough once people start doing some analytics how much of a problem this is. I don't want to see Steem becoming filled up with entropy.
I agree entirely, I also can't see any argument apart from self induglence that justifies self voting.