Although I agree with you that you haven't done anything wrong, when it comes to these sort of issues, I've learnt from experience to "dot every i and cross every t".
In other words I spell everything out in as much indisputable detail as I can.
In the case of dresses that have no belts, I always say something like, "This dress comes without a belt" or, if I model the dress in my photos with a belt of my own, I'll say: "Belt for display only - not included in sale.
That way, there is no chance of a misunderstanding or dispute.
Having said all that, you are right, if you didn't mention a belt and there was no belt in the photos of the dress, you have not mislead anyone. Its up to you, whether you want an easy life or not.
These days, I have no stomach for a fight and sellers generally come off worst in disputes on ebay anyway, so I usually take the line of least resistance and refund if that's what the buyer is requesting (unless of course, there's a very strong case against that.)
