Everyone has their own opinion about self voting, you won't find any rule or even a guideline what is acceptable on Hive as everyone has their own stake to use as they wish.
For me personally, it really depends on your stake and how often you self vote. One one hand you own the stake and can use it as you please, and why shouldn't you vote your own content and increase your rewards for your investment. On the other hand, doing so gives you an unfair advantage where you make both curation and author rewards and you remove the community from the equation.
I generally stay away from self voting but as an abuse fighter, I generally only get involved if it is unbalanced. Although I do particularly hate when people self vote comments more than anything.
This is my opinion, everyone is free to have their own and you won't find any rules or guidelines that will avoid someone downvoting you for it. It's generally best to avoid it all together and let the community decide your rewards.
Thanks for clarifying