There's no explicit code of conduct for voting, it is completely up to you how to vote and with which accounts. There's nothing for creating multiple accounts either, though steemit.com implies you should only have one account by disallowing new registrations to use previously used authenticated methods (i.e. phone number and email). However it is easy to create an account, you just have to pay for it yourself (check out Anon Steem).

However self voting was explicitly disincentivized in the founding plan of Steemit (which you can read here, though it's not an easy read and a bit out of date). So the idea was not to ban it but to make it not as worth while as voting for other people.

When the recent changes (known as hard fork 19) came in this incentive went on it's head for a few reasons:

1. The votes of people with less Steem Power became more valuable
2. Voting power depletion increased by 400%, so people could vote less at full power

Suddenly it became really attractive to vote on your own posts. Since people do what makes sense based on the evidence they have and box they are in, lots of people started doing this.

But we think this is not a good thing for the Steemit project as a whole so we're looking for solutions.

A long way to say it, but what you should do with that information, in my opinion, is talk about it like you are now and support people who are trying to do something about it.