Someone suggested this edit to one of my posts. It fixed an actual problem in the code; I had used the wrong variable in the loop, which meant my code wouldn't work. It was just intended to be a quick skeleton of an example, but still, it's nice for what's there to be correct.
Three people reviewed this and rejected it as "too minor"; one approved it. This seems to be a pretty bad decision; the review in question did fix a substantial problem in the code. In a code example, a single wrong variable can be a substantial problem; it's not minor at all.
It seems that the way the review system is set up, it encourages lots of people to do reviews (in order to get a variety of badges), but has no way to provide accountability to ensure those reviews are good. People can do reviews once they've hit a particular reputation barrier, and when you do reviews, it isn't linked at all to tags that you're active in. Now, for reviewing formatting and textual edits, that's probably fine; people with enough reputation presumably know how to use StackOverflow reasonably well and can review potential changes well. But for code changes, it generally requires someone who's familiar with the language or API in question to be able to do a good job evaluating if the fix is actually correct or not.
For answers, these problems are solved by voting and tag filtering. People generally only answer questions that they know something about, and can use tag filters to narrow in on those questions; and if they answer poorly, they are downvoted.
By emphasizing quantity of reviews with no accountability, and giving no mechanism like tag filtering so reviewers can focus on fixes in areas that they have expertise in, I feel like we're going to get a lot of bad reviews.
It looks like there's a "review audit" feature that is designed to deal with poor reviews. I can't see how I can audit this particular review, though; and again, if the people auditing a review don't have expertise in a code-change review like this, they may not be able to answer well either.