I definitely have a list of things I've let go just to be nice that have caused production outages, consistent poor performance, time-consuming technical debt,

I definitely have a list of things I've let go just to be nice that have caused production outages, consistent poor performance, time-consuming technical debt, etc. It's great to have a good relationship with your team, but at the end of the day, the things that you "let go" can become reasons not to buy your product or why new engineers won't be productive on the codebase. It's very easy to be the person that never says "no" to something, but at the same time, it's also easy to be the reviewer that doesn't advance the reviewee's career. A reviewer should ask themselves; "by not commenting on this, am I making the reviewee a better programmer?" Something I've noticed is that acquaintances will be nice to you universally, but actual friends know when to broach subjects that may not be considered "pleasant" or "nice". Don't give your friends "acquaintance-level" code reviews.