"u suck" is not feedback, it is merely offensive noise. And if you can't provide more detail, then perhaps you aren't the ideal person to be offering feedback.
"Use shadowbolt as filler until the target is <25% health" is feedback.
Does everybody see the difference between the two statements? One of them is specific and not accusatory, whereas the other one just identifies the speaker as a douchebag.
That is all.