Some of your customers may wish to communicate with you publicly right in the comments section of the product page. Potential customers may also ask you questions in private by clicking on the Ask the Designer button, which sends you an e-mail. In both cases you can answer their questions, respond to their comments and thank them for their support.
The most important factor in all this is personal relationships, which will be highly appreciated by your customers. If you give them your attention and a few minutes of your time, you will be surprised to see how they become regular customers for future designs!