diff --git a/src/utils/PhutilEditDistanceMatrix.php b/src/utils/PhutilEditDistanceMatrix.php
--- a/src/utils/PhutilEditDistanceMatrix.php
+++ b/src/utils/PhutilEditDistanceMatrix.php
@@ -54,6 +54,7 @@
   private $alterCost     = 0;
   private $maximumLength;
   private $computeString;
+  private $applySmoothing;
 
   private $x;
   private $y;
@@ -126,6 +127,15 @@
     return $this->alterCost;
   }
 
+  public function setApplySmoothing($apply_smoothing) {
+    $this->applySmoothing = $apply_smoothing;
+    return $this;
+  }
+
+  public function getApplySmoothing() {
+    return $this->applySmoothing;
+  }
+
   public function setSequences(array $x, array $y) {
 
     // NOTE: We strip common prefixes and suffixes from the inputs because
@@ -276,7 +286,13 @@
       }
     }
 
-    return $this->padEditString(strrev($str));
+    $str = strrev($str);
+
+    if ($this->getApplySmoothing()) {
+      $str = $this->applySmoothing($str);
+    }
+
+    return $this->padEditString($str);
   }
 
   private function padEditString($str) {
@@ -488,4 +504,20 @@
     }
   }
 
+  private function applySmoothing($str) {
+    $result = $str;
+
+    // Smooth the string out, by replacing short runs of similar characters
+    // with 'x' operations. This makes the result more readable to humans,
+    // since there are fewer choppy runs of short added and removed substrings.
+    do {
+      $original = $result;
+      $result = preg_replace('/([xdi])(s{3})([xdi])/', '$1xxx$3', $result);
+      $result = preg_replace('/([xdi])(s{2})([xdi])/', '$1xx$3', $result);
+      $result = preg_replace('/([xdi])(s{1})([xdi])/', '$1x$3', $result);
+    } while ($result != $original);
+
+    return $result;
+  }
+
 }
diff --git a/src/utils/PhutilProseDifferenceEngine.php b/src/utils/PhutilProseDifferenceEngine.php
--- a/src/utils/PhutilProseDifferenceEngine.php
+++ b/src/utils/PhutilProseDifferenceEngine.php
@@ -25,6 +25,12 @@
       ->setSequences($u_parts, $v_parts)
       ->setComputeString(true);
 
+    // For word-level and character-level changes, smooth the output string
+    // to reduce the choppiness of the diff.
+    if ($level > 1) {
+      $matrix->setApplySmoothing(true);
+    }
+
     $u_pos = 0;
     $v_pos = 0;
 
diff --git a/src/utils/__tests__/PhutilProseDiffTestCase.php b/src/utils/__tests__/PhutilProseDiffTestCase.php
--- a/src/utils/__tests__/PhutilProseDiffTestCase.php
+++ b/src/utils/__tests__/PhutilProseDiffTestCase.php
@@ -28,6 +28,35 @@
         '= yyy',
       ),
       pht('Remove Paragraph'));
+
+
+    // Without smoothing, the alogorithm identifies that "shark" and "cat"
+    // both contain the letter "a" and try to express this as a very
+    // fine-grained edit which replaces "sh" with "c" and then "rk" with "t".
+    // This is technically correct, but it is much easier for human viewers to
+    // parse if we smooth this into a single removal and a single addition.
+
+    $this->assertProseParts(
+      'They say the shark has nine lives.',
+      'They say the cat has nine lives.',
+      array(
+        '= They say the ',
+        '- shark',
+        '+ cat',
+        '=  has nine lives.',
+      ),
+      pht('"Shark/cat" word edit smoothenss.'));
+
+    $this->assertProseParts(
+      'Rising quickly, she says',
+      'Rising quickly, she remarks:',
+      array(
+        '= Rising quickly, she ',
+        '- says',
+        '+ remarks:',
+      ),
+      pht('"Says/remarks" word edit smoothenss.'));
+
   }
 
   private function assertProseParts($old, $new, array $expect_parts, $label) {