If this is the same as the one in the US, it reports the buyer to eBay & doesn't open a dispute.

Apparently it's meant for reporting problem buyers, such as those who just leave bad feedback without contacting the seller first, buyers who get nasty if you don't post Express when that was not an option, buyers who leave bad feedback when they obviously didn't read the description...like leaving neg or neut saying item is too big/small when dimensions/measurements are clearly & prominently shown in the listing, etc.