I was thinking that the rule I had in mind for changing to a later vote position (equivalent to unvoting and revoting with a different account) is enough of a penalty, though now that I think about it a bit, there are plenty of situations where this isn't true, especially with auction timer and large vote weight changes. But when it comes to the votes before such an adjustment, I don't see the conceptual difference between an event in which you change your vote significantly and an equivalent vote by another account that comes to shake things up.

I think complete negation of curation is too harsh of a penalty, especially in cases where one makes mistakes, which you mentioned.

I was also thinking in terms of comparisons to a multi account setup, though they are a bit hard to compare exactly. Multi account setups with the same total stake can adjust the post payout multiple times without sacrificing any curation, for example.