Someone else other than the author, may have given a randowhale vote. I have given several randowhale votes to authors I feel have been missed.

Fair point! I would give it the benefit of doubt if the vote is bought by someone else, though it'd still disincentivize curators. The lower the pending payout, the more the curation rewards.

A post that qualifies for Curie, will have an author whose vote is worth a couple of cents at best. Why should you punish someone for giving themselves such a tiny vote?

Like I mentioned above, that's no issue at all. That applies only for "significant amount". To quantify that, I'll only hesitate to vote on a self-upvoted post if its $5 or something. I might still vote it given how much I like the post. For Curie, the guideline is $2 but again, reviewers might make an exception if the post is exceptional.