Yes, we allow you the ability to respond to all reviews left on the site. If the review is positive then this just gives you the chance to thank the customer if you wish to, although you're not obliged to do so.
With negative reviews, typically you should have been in touch with the organiser prior to a public review being posted and so we would advise you to use your response to offer a further apology. If you feel the review is unfairly negative, you should use the response to explain the situation from your perspective.
Remember that your response is also public, potential customers will see this. Please remember to remain professional and refrain from using any inappropriate language.
All reviews and responses are limited to 750 characters so you will need to keep to the point.