no but most people do. You can check on https://steemworld.org/@wakeupkitty if an author is self-voting. I mean its not illegal, but many people abuse the self-vote. Its a way to make money. When you have 10 or 20 votes per day, you can make some money. In your case its 20cent per day/1,4 Dollar per Week and 73$ in one year. When the Steem price is high its maybe 730$/per year. For bigger accounts its 7000$ per year.

Nicht der Sinn der Sache