We don’t have a notion of a “negative review” on our website, the red marks unsolved financial claims to the service. Maybe it’s not the most obvious UX-design, but our service is over 15 years old, out of which for 13 years it has been exactly in this design and loyal users know about this feature.
That would mean that all other (positive) reviews available for exchanges are just solved financial claims?
I don't think your explanation is good enough, because I can clearly see people praising service, saying communication was great, and we can also see love messages...

The icon is obligatory only if KYC is obligatory for every (or for the absolute majority) of transactions. It there are random KYC-check for transactions with high level of AML-risk, we don’t make exchangers set this icon.
You need to add information for ALL exchanges with random kyc check may be performed and coins could be confiscated.
Alternative option is to say that all exchanges could ask for kyc.
Currently, our staff number has increased sufficiently to process the majority of these cases manually, that’s why we are already working on changing this system — soon exchangers will have a very limited number of attempts to lift a claim on their own, without our interference. Please wait for this update, we are already thinking about all the details.
So what happens if I create bunch of fake positive reviews and ''attack'' your system like that?
Why don't you consider that to be abuse in the same way like you consider ALL negative reviews?
For example, I could hire bunch of people to make minimal transaction and write 100 or more positive reviews for openchange or any other exchange I want.