Sometimes when the reason is not obvious we will email the reviewer their review is deleted and they can write again. For everything else it is already in the review guidelines
. If they read it they wouldn't be writing a review that does not fit the review guidelines, if they didn't read the guidelines what make you think they will read the email reason for deletion.
Other reason for review missing is the account is not the only account of the reviewer which need to be removed.
We will not email the server owner directly because there is conflict of interest and increase chance of giving incentive for review behind the scene.
For the review deleted in your screenshot, note that "One of the best servers I've played on in the 16 years I've been playing RO." and "Fantastic server" is not considered as review content but promotional content. That goes half of the review leaving "great player environment. A lot of helpful people chat on #main supporting both new and veteran players alike." to support that given score. It is shorter than the minimum character requirement for a review and there are a lot more spaces available. Yes, we expect a little more than that if the reviewer thinks the server is perfect or close to perfect.
When reading reviews, I often ask the question "How does this review give information or share an experience of the server that will help the next person reading it know more about what's going on in the server and decide if this server fits him or her?"