It's a hotly debated topic for sure. My personal opinion is that if their vote is low enough, then I don't care. I curate as normal. However, if their stake is high enough to allow a significant level of rewards, then I won't downvote, but I won't curate either.

Self-votes were allowed and even recommended in the past to demonstrate that the author believes in their work. Now, it's not allowed because whales in the past abused the system. Currently, there is a negative stigma against the practice. I ignore that stigma unless the rewards become significant.