I would think the answer above this one sums it up pretty well.

I have never written 'avoid, avoid' on anyone's feedback, nor have I given neutral or negative, even though I am 99.9% a buyer.

But over the last few months, I have added any downsides in with the positives, mainly so other buyers will know the score.

There have been times when some sellers were pretty lucky, I reckon, that I gave them positive, but I pretty much stick to positive if I got the goods (or even when it's only something sort of like the goods, which is what happened with a lot of pots I bought 🙂 )

But you are right, feedback is most useful if it is honest & balanced. Not much use putting completely negative comments and giving a positive.