When you're responding to customers, try to focus on detractors first. These are customers/users at-risk and a large portion of them will churn in a 90-day period without engagement. Address immediate issues that were highlighted by them in their feedback and follow-up to dig in further if they did not leave a comment.
Anyone in the Detractor (0-6) and Passive (7-8) range who did not leave comments you definitely want to follow-up with and try to isolate the main issue. For detractors you may simply want to ask "What can we do to help?" and for the passives, here is a line that many of our customers use:
"Please let us know what we could do to earn your recommendation in the future."
For Promoters (9-10's) you absolutely want to thank them whether or not they left comments, and every single promoter you should have an “ask” if you can. This is specific to every business so it's hard to make suggestions, but this may be as simple as asking for a social media post (tweet, Facebook post, etc.), an online review, direct referrals they might have, etc.