It seems to me that there are two points here:
1. You had a bad experience with a seller and wished to share this & want to stop others using this particular seller;
2. You want everyone to agree with you that this seller is at fault, and their feedback shows how bad they are?
In connection with point 1, Yes the seller made a mistake, however, as per the terms of eBay, they are offering you a full refund. Fine to raise the issue, but others have had good experiences, stated this, but you still want them not to use this seller.
In connection with point 2, when you post on a forum, not everyone is going to agree with you, no point posting if everyone agreed. An open discussion should be expected, with points made in a clear and logical way, to maximise your point of view. Posts containing limited information will induce conjecture, and increase speculation. The seller has some negative feedback, but out of 27,000 items in the past 12 months and as I have already stated, the number of negatives is small. In an ideal world everything would be 100% with no negatives etc etc etc. However, the real world is slightly different and there will be issues. It is how these are corrected that is important and it seems to me a full refund has been offered which is what the eBay rules state.