A few things.
TER could probably solve this stuff by removing the top and botton 2 scores (once someone reaches a number of reviews). Basic extrapolation to toss out the outliers. Scientists do this for a reason, there are always outliers, and it would offset a lot of angst. In a situation like this, the provide rating would be intact, and the review would remain. If you have 30 reviews and 1 is bad, it would be ignored. Likewise, if you have 30 of the 8/8 reviews and one 10/10, it would also be ignored from the score, but again, the review would still be there for people to read.
Second, It's clear to me from the history of reviews that this one is an outlier, I think most of us would toss that rating out mentally anyway. Even better, the review itself was positive. In fact, after seeing the reviews if anything I am intrigued
Could very well be someone trying to get free membership. Quite honestly, TER should do away with the free membership for reviews, it's a clear conflict of interest. If anything, maybe free TER months based on the number of LIKES your review gets. Good, well written reviews that help the community should be rewarded, not just a few lines of drivel.
Peace