Hello, I just wrote a small Magento extension to allow you the single sign-on between you Magento ecommerce site and your Uservoice support site.
Based upon the original Uservoice documentation, you can install it (just copy the files into your Magento folder), you will find a new configuration settings under the left sidebar “USERVOICE SINGLE SIGN-ON“.
uv.src = ('https:' == document.location.protocol ? 'https://' : 'http://') + 'widget.uservoice.com/EyMQSdgfLyXVzREO2N55P7A.js‘;”
You can find the Magento extension for Uservoice on my GitHub repository.