Adding comment to prevent issue #735

src/styles/brackets_theme_default.less

@@ -103,6 +103,8 @@
 .code-font() {
     color: @content-color;
     pre {
+        // line-height must be specified in px not em because the code font and line number font sizes are different.
+        // Sizing via em will cause the code and line numbers to misalign
         line-height: 15px;
     }
 }