In my company some teams report problems found in code review using collaborative code review tools like Crucible. Those allow to share comments about the code inline and integrate easily with IDE.
Our architect sometimes send e-mails with code review results and they go through grooming and are included in the backlog of stories to do.
I, as a tester, try to avoid commenting pure technical debt. I rather report code review issues when they could result in breaking some functionality. Most issues are found during iteration, so I report them it in our iteration tracking/planning portal.
Regarding your question about usefulness, I had related question in the past: Is it fair to report a bug discovered during review without performing a test?, (which is rather about usefulness than fairness) and one of the main conclusions was that it might be more convincing to developers, if you confirm issue found in code review with a test