Please quit trying to lay down the law regarding what reviewers should or should not do whilst reviewing.
Firstly because it's not your place: you don't own or run the reviewing sites, so you don't get to make the rules. More importantly, though, is the fact that there will never be a consensus among you. I know that, because every time one author puts a rule forward, another author refutes it:
Some authors insist that it's unfair to write DNF reviews, while others mock readers who bother to finish a book they hate.
Some authors complain about the lack of text in reviews, while others complain about reviews being too long.
Some authors demand constructive criticism, and others feel harassed when it's offered.
And really what all this haranguing over reviews amounts to is: If a reader doesn't like your book, you want them to be quiet about it. That's all. That's the truth. The rules are just excuses. Possibly excuses you have told yourselves:
- If that person had read the whole book, I'm sure they would have given me a better rating.
- If that reader had stopped when they realized my book wasn't for them, they wouldn't have given me a bad rating.
- I don't mind negative reviews, so long as the reasons are well documented and thus refutable.
- I don't mind negative reviews, except when they point out so many mistakes it's insulting.
- I wouldn't mind negative reviews if they were constructive.
- I don't mind negative reviews, but who is this reader to tell me what I could do to improve?
Not only is this behavior annoying to readers, but it's not a sustainable method for dealing with negative reviews, either. Sooner or later, someone will say something in a review that you cannot pigeonhole and dismiss. They'll point out something you can't deny.
Rather than coming up with excuses for why the review is wrong, you need to be fine with negative reviews regardless. They happen. If you're happy with your writing, and you're making enough sales to be satisfied, then who cares what your reviews say? But if you're not, then maybe the reviews could give you a clue as to why, and maybe you should pay attention, rather than closing your eyes and hoping they'll go away.
Not that reviews have to be constructive. That's more a bonus than anything. But that doesn't mean they can't provide insight into what you're doing wrong, just the same.
Think about it. Please? It's far easier to change what you are doing than to change what millions of readers might do.