If we're recommending stuff, please just make the rule that you can't vote for your own entry (pizza, pumpkin, whatever) official going forward.
My blood boils a bit after every 'can I vote for myself' question. No, you can't, not sure what sort of a contestant even asks something like this.
Let the blood boil. That seems to be on you.

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We can agree to disagree.
i don't see anything wrong with a participant voting for his own pizza, if he were to have a pizza in the contest, if he were eligible to vote, and if he were to choose to vote for his own pizza.
Coordinated voting is problematic, so I am not sure how to address it fairly.. though it may well be in the discretion of the contest coordinator to come to such judgement regarding the appearance of impropriety.... yet, it still becomes difficult to address such a thing in terms of if adaptations are attempted to be more subtle in such coordinated votes... There does seem to be a bit of a dilemma regarding whether and/or how to address such a situation for this time around and/or for future contests.
It is pretty nice to be able to have these kinds of contests, yet at the same time, it would be shame to see them either go away or to cause derision due to perceptions of unfairness.