[abhi9u]

I take your point that it could have been more strongly worded. The reason I say it "devliers unexpectedly well" is because the whole concept of using gzip for classification is unintuitive, and even after fixing the flaw it still manages to get decent accuracy (given that it is no more beating state-of-the-art models).

[liliumregale]

Further analysis shows that it doesn’t perform well at all—successes are tied to things like test set leakage.

https://kenschutte.com/gzip-knn-paper2/

This paper isn’t any surprisingly effective result. It’s thoroughly shoddy scholarship by which the authors should feel embarrassed.