[to11mtm]

Depends on the overall rapport.

"you're sloppy" is too personal.

"this is not to the standard what I would expect" with reasons is factual, if, having been on the receiving end of, harsh. But it should not be done publicly.

"This has to be changed because it will break" (on a PR) is perfectly fine.

"This wasn't even run through linter, please don't drive folks to force push hooks" can be 3rd person passive aggressive (e.x. I'm not advocating for them but others want a series of hooks that is just...too...much...) but potentially factual.

"This .cs file was 2500 lines. You were given a choice but instead you chose violence" is something that was very very hard to not reword into something more polite when a PR wanted to add another 2600 lines. At the very least turn it into a more constructive "This .cs file is already 2500 lines. We need to stop the violence and refactor the class per-business-aspect."

I like that last example, because it shows some very subtle differences in how the same information can be communicated while severity/importance is still pretty dang clear.