Expanding Javadoc from #1454 as suggested by @oleg-nenashev.

core/src/main/java/hudson/model/Computer.java

@@ -1313,7 +1313,7 @@ public /*transient*/ abstract class Computer extends Actionable implements Acces
      * Gets the current {@link Computer} that the build is running.
      * This method only works when called during a build, such as by
      * {@link hudson.tasks.Publisher}, {@link hudson.tasks.BuildWrapper}, etc.
-     * @return the {@link Computer} associated with {@link Executor#currentExecutor}, or null if not on an executor thread
+     * @return the {@link Computer} associated with {@link Executor#currentExecutor}, or (consistently as of 1.591) null if not on an executor thread
      */
     public static @Nullable Computer currentComputer() {
         Executor e = Executor.currentExecutor();