diff --git a/search/search_quality/assessment_tool/context.cpp b/search/search_quality/assessment_tool/context.cpp
index ec69243651..595541b093 100644
--- a/search/search_quality/assessment_tool/context.cpp
+++ b/search/search_quality/assessment_tool/context.cpp
@@ -63,7 +63,6 @@ search::Sample Context::MakeSample(search::FeatureLoader & loader) const
       continue;
     }
 
-    // No need to keep irrelevant results.
     if (foundEntries[j].m_curr.m_unknown)
       continue;
 
@@ -82,7 +81,6 @@ search::Sample Context::MakeSample(search::FeatureLoader & loader) const
       continue;
     }
 
-    // No need to keep irrelevant results.
     if (foundEntries[i].m_curr.m_unknown)
       continue;
 
diff --git a/search/search_quality/assessment_tool/edits.hpp b/search/search_quality/assessment_tool/edits.hpp
index 68e2763d8c..038a747b90 100644
--- a/search/search_quality/assessment_tool/edits.hpp
+++ b/search/search_quality/assessment_tool/edits.hpp
@@ -37,6 +37,12 @@ public:
     bool operator!=(MaybeRelevance const & rhs) const { return !(*this == rhs); }
 
     Relevance m_relevance = Relevance::Irrelevant;
+    // The guard for |m_relevance|. The |m_relevance| field
+    // should be read only when |m_unknown| is false.
+    // It is implemented as a separate guard instead of another value
+    // in the Relevance's enum because it results in cleaner typing
+    // in our case (we only use unknown in the UI, so serializing
+    // it makes no sense).
     bool m_unknown = true;
   };