I had an incident many years ago where I found glaring design flaws in a much more senior developer's code, and, overcome with some feeling of superiority, left a million nitpicky comments and a snide summary, then posted on our team chat "left a review". Finally, I was getting back at all the senior developers who had torn apart my code. I later realized my comments were mean and I apologized. While you could still potentially call it constructive criticism, there is a difference between mean criticism and polite criticism.

I do think thorough feedback is important, that's how I've learned the most after all. But typically now if I I'm going to write more than 5 comments, I meet with the other developer in person instead. That way the code problems are solved faster and it avoids any sort of public humiliation.