As a buyer I get very frustrated when I do not get any answer to emails, be it questions about an item before I bid, or buy, enquiries about late delivery, or problems with the item when I have received it.
A quick response to a question whilst the listing is active can mean more buy it now sales, or more bids on an auction item, resulting in a higher closing value.
Even more important is handling complaints about non delivery or problems with the goods, in other words after sales service. I am amazed by the number of sellers who ignore these emails only to earn themselves negative feedback.
How often have you seen “Waited ages, goods not as described, ignored emails?”
This is very often followed some feeble excuse in the response from seller. It is even worse when in some cases the seller starts slanging off the buyer. I always keep well clear of these sellers.
If you put communication at the top of your important things list, it is very unlikely that you will receive any negative feedback. In the event that having done your best you are dealing with a buyer who does not give you the opportunity to rectify any mistake, and leaves negative feedback, do not retaliate, it might make you feel better, but it most probably will put other prospective buyers off.
The best way to follow up is an apology, and a full refund, but never make up some feeble excuse, this can only do more harm than good.