diff --git a/icu4c/source/i18n/number_fluent.cpp b/icu4c/source/i18n/number_fluent.cpp
index 198c7caee0f..e0e489a3573 100644
--- a/icu4c/source/i18n/number_fluent.cpp
+++ b/icu4c/source/i18n/number_fluent.cpp
@@ -363,6 +363,7 @@ UnlocalizedNumberFormatter::UnlocalizedNumberFormatter(const NFS<UNF>& other)
     // No additional fields to assign
 }
 
+// Make default copy constructor call the NumberFormatterSettings copy constructor.
 UnlocalizedNumberFormatter::UnlocalizedNumberFormatter(UNF&& src) U_NOEXCEPT
         : UNF(static_cast<NFS<UNF>&&>(src)) {}
 
@@ -383,6 +384,7 @@ UnlocalizedNumberFormatter& UnlocalizedNumberFormatter::operator=(UNF&& src) U_N
     return *this;
 }
 
+// Make default copy constructor call the NumberFormatterSettings copy constructor.
 LocalizedNumberFormatter::LocalizedNumberFormatter(const LNF& other)
         : LNF(static_cast<const NFS<LNF>&>(other)) {}
 
diff --git a/icu4c/source/i18n/numrange_fluent.cpp b/icu4c/source/i18n/numrange_fluent.cpp
index ec00588502e..aee9518fe09 100644
--- a/icu4c/source/i18n/numrange_fluent.cpp
+++ b/icu4c/source/i18n/numrange_fluent.cpp
@@ -3,7 +3,7 @@
 
 #include "unicode/utypes.h"
 
-#if !UCONFIG_NO_FORMATTING && !UPRV_INCOMPLETE_CPP11_SUPPORT
+#if !UCONFIG_NO_FORMATTING
 
 // Allow implicit conversion from char16_t* to UnicodeString for this file:
 // Helpful in toString methods and elsewhere.
@@ -192,6 +192,7 @@ UnlocalizedNumberRangeFormatter::UnlocalizedNumberRangeFormatter(const NFS<UNF>&
     // No additional fields to assign
 }
 
+// Make default copy constructor call the NumberRangeFormatterSettings copy constructor.
 UnlocalizedNumberRangeFormatter::UnlocalizedNumberRangeFormatter(UNF&& src) U_NOEXCEPT
         : UNF(static_cast<NFS<UNF>&&>(src)) {}
 
@@ -212,6 +213,7 @@ UnlocalizedNumberRangeFormatter& UnlocalizedNumberRangeFormatter::operator=(UNF&
     return *this;
 }
 
+// Make default copy constructor call the NumberRangeFormatterSettings copy constructor.
 LocalizedNumberRangeFormatter::LocalizedNumberRangeFormatter(const LNF& other)
         : LNF(static_cast<const NFS<LNF>&>(other)) {}
 
diff --git a/icu4c/source/i18n/numrange_impl.cpp b/icu4c/source/i18n/numrange_impl.cpp
index 140effaaa64..b240c3140d6 100644
--- a/icu4c/source/i18n/numrange_impl.cpp
+++ b/icu4c/source/i18n/numrange_impl.cpp
@@ -3,7 +3,7 @@
 
 #include "unicode/utypes.h"
 
-#if !UCONFIG_NO_FORMATTING && !UPRV_INCOMPLETE_CPP11_SUPPORT
+#if !UCONFIG_NO_FORMATTING
 
 // Allow implicit conversion from char16_t* to UnicodeString for this file:
 // Helpful in toString methods and elsewhere.
@@ -181,6 +181,7 @@ NumberRangeFormatterImpl::NumberRangeFormatterImpl(const RangeMacroProps& macros
     // this part of the code should be updated to load from the local numbering system.
     // The numbering system could come from the one specified in the NumberFormatter passed to
     // numberFormatterBoth() or similar.
+    // See ICU-20144
 
     NumberRangeData data;
     getNumberRangeData(macros.locale.getName(), "latn", data, status);
diff --git a/icu4c/source/i18n/numrange_impl.h b/icu4c/source/i18n/numrange_impl.h
index c763f0c72c5..787fc656860 100644
--- a/icu4c/source/i18n/numrange_impl.h
+++ b/icu4c/source/i18n/numrange_impl.h
@@ -20,13 +20,10 @@ namespace impl {
 
 
 /**
- * Implementation class for UFormattedNumber with magic number for safety.
+ * Class similar to UFormattedNumberData.
  *
- * This struct is also held internally by the C++ version FormattedNumber since the member types are not
- * declared in the public header file.
- *
- * The DecimalQuantity is not currently being used by FormattedNumber, but at some point it could be used
- * to add a toDecNumber() or similar method.
+ * Has incomplete magic number logic that will need to be finished
+ * if this is to be exposed as C API in the future.
  */
 struct UFormattedNumberRangeData : public UMemory {
     // The magic number to identify incoming objects.
diff --git a/icu4c/source/i18n/unicode/numberformatter.h b/icu4c/source/i18n/unicode/numberformatter.h
index b742e9104f1..b75d8e6432f 100644
--- a/icu4c/source/i18n/unicode/numberformatter.h
+++ b/icu4c/source/i18n/unicode/numberformatter.h
@@ -2157,7 +2157,6 @@ class U_I18N_API UnlocalizedNumberFormatter
      */
     UnlocalizedNumberFormatter() = default;
 
-    // Make default copy constructor call the NumberFormatterSettings copy constructor.
     /**
      * Returns a copy of this UnlocalizedNumberFormatter.
      * @draft ICU 60
@@ -2296,7 +2295,6 @@ class U_I18N_API LocalizedNumberFormatter
      */
     LocalizedNumberFormatter() = default;
 
-    // Make default copy constructor call the NumberFormatterSettings copy constructor.
     /**
      * Returns a copy of this LocalizedNumberFormatter.
      * @draft ICU 60
diff --git a/icu4c/source/i18n/unicode/numberrangeformatter.h b/icu4c/source/i18n/unicode/numberrangeformatter.h
index 30a7c1e8050..5b9f264f9bf 100644
--- a/icu4c/source/i18n/unicode/numberrangeformatter.h
+++ b/icu4c/source/i18n/unicode/numberrangeformatter.h
@@ -493,7 +493,6 @@ class U_I18N_API UnlocalizedNumberRangeFormatter
      */
     UnlocalizedNumberRangeFormatter() = default;
 
-    // Make default copy constructor call the NumberFormatterSettings copy constructor.
     /**
      * Returns a copy of this UnlocalizedNumberRangeFormatter.
      * @draft ICU 63
@@ -566,7 +565,6 @@ class U_I18N_API LocalizedNumberRangeFormatter
      */
     LocalizedNumberRangeFormatter() = default;
 
-    // Make default copy constructor call the NumberRangeFormatterSettings copy constructor.
     /**
      * Returns a copy of this LocalizedNumberRangeFormatter.
      * @draft ICU 63
diff --git a/icu4j/main/classes/core/src/com/ibm/icu/number/NumberRangeFormatterImpl.java b/icu4j/main/classes/core/src/com/ibm/icu/number/NumberRangeFormatterImpl.java
index 1a43f85f36e..cdccb5e6df6 100644
--- a/icu4j/main/classes/core/src/com/ibm/icu/number/NumberRangeFormatterImpl.java
+++ b/icu4j/main/classes/core/src/com/ibm/icu/number/NumberRangeFormatterImpl.java
@@ -120,6 +120,7 @@ class NumberRangeFormatterImpl {
         // this part of the code should be updated to load from the local numbering system.
         // The numbering system could come from the one specified in the NumberFormatter passed to
         // numberFormatterBoth() or similar.
+        // See ICU-20144
 
         getNumberRangeData(macros.loc, "latn", this);