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.