I’m a big numbers person and wouldn’t delete reviews even if they were flames because hey, at least they reviewed!
My first flame was on my first Sailor Moon/Dragonball Z crossover that I co-wrote with an old friend in 2002 when I was 14.
If I recall correctly, fans of my fic messaged the flamer endlessly until they apologized. Later on, they came back (probably 6 months later) and gave a constructive feedback review that outlined how I could improve, what was wrong, and areas that I needed to work on. I appreciate that this person did come back later and give me constructive feedback. It’s probably one of my most memorable flames and later constructive feedback reviews.