First:
When @Sadkitten downvotes my Comments or Posts because I upvoted it by myself it doesn´t only hurt me. It also hurts everyone who has allready upvoted my Comments or Posts and will normally get his Part of the Payout. With a downvote of @Sadkitten not only the Part that I get as a reward but also the reward of other Upvoters is getting decreased dramatically.
Second:
@Sadkitten downvotes Posts and Comments with the intention that I don´t give enough to the community if I self upvote my posts. With a self upvote I increase the reward from other upvotes, that´s also a kind of giving back. When @Sadkitten downvotes my Comments and Posts it decreases the rewards for other users. I think it´s really paradox to think that decreasing rewards for other users will help them to get more.
Third:
I invested several thousand Euros in Steemit and I´m upvoting and commenting at several posts almost every day.
Fourth:
We are on Steemit where everyone is free to do whatever she or he wants.
Feel free to comment and share, because I´m really interested what you think about @Sadkitten and self upvoting.