The Code Review Mistakes Even Senior Developers Make

I've given and received thousands of code reviews. I've made every mistake on this list, usually multiple times.

Code review seems simple: look at code, find problems, write comments. But effective code review is surprisingly difficult. Even experienced developers fall into patterns that make reviews less useful—or actively harmful.

Here are the mistakes I see most often, including from developers who should know better.

Mistake 1: Reviewing Too Much at Once

A 50-line change is easy to review carefully. A 500-line change overwhelms reviewers. A 5000-line change? Nobody reviews that properly.

Research confirms this: defect detection drops dramatically as review size increases. Beyond a few hundred lines, reviewers miss things. Important things.

But developers keep submitting huge changes. And reviewers keep "approving" them after superficial scans.

The fix: Break large changes into smaller, logical pieces. Review incrementally. If someone submits a massive change, ask them to split it—not because you're being difficult, but because you literally cannot review it well.

Mistake 2: Focusing on Style Over Substance

It's easy to spot a missing semicolon or inconsistent indentation. It's hard to evaluate whether an algorithm is correct or an architecture is sound.

So reviews drift toward style comments. "Add a blank line here." "Rename this variable." "This brace should be on the next line."

These comments aren't wrong, but they're low value. Automated tools catch style issues better than humans. Your attention should focus on what automation can't catch.

The fix: Let linters and formatters handle style. Reserve your attention for logic, architecture, security, and other issues that require human judgment.

Mistake 3: Demanding Your Preferred Solution

"This works, but I would have done it differently."

Everyone has preferences. But code review isn't about making code match your preferences. It's about ensuring code meets quality standards.

If code works, is readable, performs acceptably, and follows team conventions—it's probably fine. Even if you'd have written it differently.

The fix: Before commenting, ask: "Is this wrong, or just different from what I would do?" Block merges for wrong. Make suggestions for different. There's a distinction.

Mistake 4: Not Providing Context

"This is bad."
"Why?"
"It just is."

Unhelpful comments frustrate authors and don't help them improve. If you can't explain why something is problematic, maybe it's not as problematic as you thought.

The fix: Every critique needs a reason. "This could cause a null pointer exception because X returns null when Y" is actionable. "This is bad" is not.

Mistake 5: Blocking on Nitpicks

Some issues are blocking: security vulnerabilities, bugs, broken functionality. The code shouldn't merge until they're fixed.

Some issues are suggestions: possible improvements, alternative approaches, minor cleanups. The code can merge without them.

Mixing these categories frustrates everyone. Authors don't know what's actually required. Reviewers get a reputation for blocking on trivia.

The fix: Be explicit about what's blocking versus what's optional. "This needs to change before merge" versus "Consider doing X, but up to you."

Mistake 6: Delayed Reviews

A review that arrives three days late is worth less than a review that arrives in three hours.

When reviews are slow, developers context-switch to other work. When feedback finally arrives, they have to reload mental context. Changes are harder to make. Understanding is harder to recover.

Slow reviews also clog pipelines. Work stacks up waiting for review while reviewers attend to "more important" things.

The fix: Prioritize review as real work, not interruption. Set expectations for review turnaround time. If you can't review promptly, say so rather than leaving it in limbo.

Mistake 7: Not Actually Running the Code

Reading code is different from running code. You can miss obvious problems by only reading.

Does the feature actually work? Does it handle edge cases? Is the performance acceptable? You won't know until you try it.

The fix: For significant changes, actually run the code. Check out the branch, exercise the feature, verify it does what it claims. This catches problems reading misses.

Mistake 8: Rubber Stamping

"LGTM" after thirty seconds on a complex change isn't a review. It's theater.

Rubber stamping happens when reviewers are busy, when they trust the author too much, or when they don't feel qualified to review the code.

But rubber stamps provide false confidence. Problems slip through. The code was "reviewed"—but not really.

The fix: If you don't have time to review properly, say so. If you're not qualified, find someone who is. An honest "I can't review this effectively" is better than a fake approval.

Mistake 9: Making It Personal

"This code is sloppy" attacks the author.
"This code has a bug on line 42" addresses the code.

The difference matters. Code review is stressful. Authors are vulnerable. Personal attacks—even mild ones—create defensiveness and damage relationships.

The fix: Critique the code, not the person. Assume good intent. Phrase feedback as observations about the code rather than judgments about the author.

Mistake 10: Not Recognizing Good Work

Reviews often focus entirely on problems. Find the bugs. Spot the issues. Flag the concerns.

This creates an environment where code review feels like criticism. Authors dread reviews rather than valuing them.

The fix: Call out good work too. "Nice refactoring here." "This error handling is thorough." "Clever solution." Positive feedback encourages good practices and makes the review process less adversarial.

Mistake 11: Ignoring Tests

Code comes with tests. Do the tests actually verify the code works? Are there important cases the tests miss? Are the tests themselves well-written?

Most reviewers focus on production code and skim the tests. This is backwards—tests are how you know production code works.

The fix: Review tests as carefully as production code. Check that they test the right things. Look for missing cases. Consider whether the tests would catch likely bugs.

Mistake 12: No Follow-Through

You leave comments. Author makes changes. You... never look again.

---

📖 Read the full article with code examples and detailed explanations: kobraapi.com

This article was refined with the help of AI tools to improve clarity and readability.