Self upvote option is there for a reason. There is nothing wrong in using it (my opinion). My voting power is zero but I do upvote my posts. Same reason as you gave. And after reading this post, I'm encouraged to upvote people's comment as well. Initially, I thought there's no need of me to upvote others with zero power. But you have changed my mind. No matter what's your voting power, upvote is an act of engagement.
Here's my graph. I had been in-active for a month. I have resumed since last week so my stats are pretty low.