Currently the only way for a developer to respond to a user comment about their Alexa Skill is via comments in the review section.
Now the only people who can comment or otherwise respond to a review are those who have spent a certain amount of money (for the US it is $50) on that particular amazon site. Clearly a developer publishing in multiple languages in different international locales would not have spent enough money in most international locales other their own home, so they can't respond to any comments posted for their international versions. This is a glaring hole and very demoralizing for developers, since often the comments are based on not understanding the skill. Amazon's suggestion was to leave your contact info in the skill description, we did, but still a user's first instinct on running into problems is to leave a bad review.