Re. civility, I've had very good results in reducing stress between both parties by clearly separating the defects in the work from the person / people involved. I think that's the key because I've had terrible experiences when that did not happen, when I was either blaming or blamed (seemingly) by teammates personally for any mistakes. Still, I'd rather receive any honest feedback than none at all, even if it is presented incorrectly and callous. Holding back feedback to be nice can grow problems and erode trust.