Review comment fixes and more small improvements.

core/src/main/resources/jenkins/model/Jenkins/help-rawBuildsDir.html

 <div>
-    Specify where Jenkins should store build records. This includes the console
-    output and other metadata generated by a build.
+    Specifies where Jenkins will store build records on the file system. This
+    includes the console output and other metadata generated by a build.
     <p>
-    This value can include the following variables:
+    This value may include the following variables:
     <ul>
-        <li><tt>${JENKINS_HOME}</tt> &mdash; The Jenkins home directory
-        <li><tt>${ITEM_ROOTDIR}</tt> &mdash; The directory where Jenkins stores config data for a given job
+        <li><tt>${JENKINS_HOME}</tt> &mdash; Absolute path of the Jenkins home
+            directory
+        <li><tt>${ITEM_ROOTDIR}</tt> &mdash; Absolute path of the directory
+            where Jenkins stores the configuration and related metadata for a
+            given job
         <li><tt>${ITEM_FULL_NAME}</tt> &mdash; The full name of a given job,
             which may be slash-separated, e.g. <tt>foo/bar</tt> for the job
             <tt>bar</tt> in folder <tt>foo</tt>
@@ -17,5 +20,9 @@
     Changing this value allows you to store build records on a larger, but
     slower disk, rather than on the same disk where builds are executed.
     <p>
+    Any changes to this value will take effect as soon as this configuration
+    page is saved, but note that Jenkins will not automatically migrate any data
+    from the current build record root directory.
+    <p>
     The default value is <tt>${ITEM_ROOTDIR}/builds</tt>.
 </div>

core/src/main/resources/jenkins/model/Jenkins/help-rawWorkspaceDir.html

 <div>
-    Specify where Jenkins should store workspaces for builds that are executed
+    Specifies where Jenkins will store workspaces for builds that are executed
     on the master.<br>
     It has no effect on builds that are executed on agents.
     <p>
-    This value can include the following variables:
+    This value may include the following variables:
     <ul>
-        <li><tt>${JENKINS_HOME}</tt> &mdash; The Jenkins home directory
-        <li><tt>${ITEM_ROOTDIR}</tt> &mdash; The directory where Jenkins stores config data for a given job
+        <li><tt>${JENKINS_HOME}</tt> &mdash; Absolute path of the Jenkins home
+            directory
+        <li><tt>${ITEM_ROOTDIR}</tt> &mdash; Absolute path of the directory
+            where Jenkins stores the configuration and related metadata for a
+            given job
         <li><tt>${ITEM_FULL_NAME}</tt> &mdash; The full name of a given job,
             which may be slash-separated, e.g. <tt>foo/bar</tt> for the job
             <tt>bar</tt> in folder <tt>foo</tt>
@@ -19,5 +22,9 @@
     put build workspaces on faster storage hardware, such as SSDs or even RAM
     disks.
     <p>
+    Any changes to this value will take effect as soon as this configuration
+    page is saved, but note that Jenkins will not automatically migrate any data
+    from the current workspace root directory.
+    <p>
     The default value is <tt>${ITEM_ROOTDIR}/workspace</tt>.
 </div>

war/src/main/webapp/help/system-config/homeDirectory.html

 <div>
-  Jenkins stores all of its data in this directory on the file system.
+  By default, Jenkins stores all of its data in this directory on the file
+  system.
   <br>
-  There are a few ways to change this directory:
+  Under the <i>Advanced</i> section, you can choose to store build workspaces
+  and build records elsewhere.
+  <p>
+  There are a few ways to change the Jenkins home directory:
   <ul>
     <li>
       Edit the <code>JENKINS_HOME</code> variable in your Jenkins configuration
-      file (e.g. <code>/etc/sysconfig/jenkins</code> on Red Hat).
+      file (e.g. <code>/etc/sysconfig/jenkins</code> on Red Hat Linux).
     <li>
       Use your web container's admin tool to set the <code>JENKINS_HOME</code>
       environment variable.
     <li>
       Set the environment variable <code>JENKINS_HOME</code> before launching
       your web container, or before launching Jenkins directly from the WAR file.
+    <li>
+      Set the <code>JENKINS_HOME</code> Java system property when launching your
+      web container, or when launching Jenkins directly from the WAR file.
     <li>
       Modify <tt>web.xml</tt> in <tt>jenkins.war</tt> (or its expanded image in
       your web container). This is not recommended.