How do I unselect a "best answer" comment from my MOSC post?

It is easy to select a response as helpful... but I can't find any method/documentation to uncheck a response. I selected an answer that appeared to be correct, but one month later the problem resurfaced so that solution is clearly not the answer. I added an update indicating the problem resurfaced and checked that as helpful, hoping it would replace the first answer, but it just added it to a list of "best answers". So... now I want to uncheck both. The correct "best answer" is currently no answer.

Short of creating an SR to ask this question, I can't figure how how to get to "Oracle" to ask this question.