As the code reviewer you should probably not be doing any writing. Instead, you should send back the code with notes. An in-person meeting would be better to go

As the code reviewer you should probably not be doing any writing. Instead, you should send back the code with notes. An in-person meeting would be better to go over the changes. Teach a man to code, he can write crappy code. Fix it for him, he still writes crappy code. Make him fix it himself, he learns (hopefully). Also, as a code reviewer myself, this is really difficult, but the best way to fix this kind of thing in the future is to get involved in the code much earlier on. Watch the commits as they get made, stop by occasionally and go over the code while it's in progress. If the guy spends a week working on something and you send it back, he basically wasted a week. If you can spot a problem within a few hours, then you saved both of you a week...