Is there some simple extension that would allow me to reply to customer product review from admin panel or admin account so everyone could see it?
Have look on our advance product testimonials extension that allows your to not only reply the customer reviews but also allows your other customers to rate, like & reply existing product reviews.
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Additionally in next major release it's planned to add an ability to post comments to reviews from any user (administration responses will be marked additionally).
We have solution for you - Our plugin "Extended Product Reviews" https://www.magentocommerce.com/magento-connect/extended-reviews-with-reminder.html
did you try out this extension,
from simple to advance features, you can customize it easily as per your needs,
The upcoming product by Aheadworks - the Advanced Reviews extension for Magento 2 - provides such kind of functionality.
After a review is approved, it's possible for a store admin to leave a comment. The module also enables the 'Review summary block' functionality for demonstration review summaries. So, that admin comments on the reviews will be visible.