Run.whyKeepLog should be a complete sentence.

Otherwise you get nonsense like this:
Cannot delete this build, because it is #3 depends on this

core/src/main/java/hudson/matrix/MatrixBuild.java

@@ -247,7 +247,7 @@ public class MatrixBuild extends AbstractBuild<MatrixProject,MatrixBuild> {
     public String getWhyKeepLog() {
         MatrixBuild b = getNextBuild();
         if (isLinkedBy(b))
-            return b.getDisplayName()+" depends on this";
+            return Messages.MatrixBuild_depends_on_this(b.getDisplayName());
         return super.getWhyKeepLog();
     }
 

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

@@ -528,8 +528,8 @@ public abstract class Run <JobT extends Job<JobT,RunT>,RunT extends Run<JobT,Run
     }
 
     /**
-     * If {@link #isKeepLog()} returns true, returns a human readable
-     * one-line string that explains why it's being kept.
+     * If {@link #isKeepLog()} returns true, returns a short, human-readable
+     * sentence that explains why it's being kept.
      */
     public String getWhyKeepLog() {
         if(keepLog)

core/src/main/resources/hudson/matrix/MatrixBuild/confirmDeleteAll.properties

@@ -20,4 +20,4 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 # THE SOFTWARE.
 
-cannotMsg=Cannot delete this build, because it is {0}
+cannotMsg=Cannot delete this build: {0}

core/src/main/resources/hudson/matrix/Messages.properties

@@ -20,6 +20,7 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 # THE SOFTWARE.
 
+MatrixBuild.depends_on_this={0} depends on this.
 MatrixProject.DisplayName=Build multi-configuration project
 MatrixProject.DuplicateAxisName=Duplicate axis name
 
@@ -36,4 +37,4 @@ MatrixRun.KeptBecauseOfParent=Kept because {0} is kept
 JDKAxis.DisplayName=JDK
 LabelAxis.DisplayName=Slaves
 LabelExpAxis.DisplayName=Label expression
-TextArea.DisplayName=User-defined Axis
\ No newline at end of file
+TextArea.DisplayName=User-defined Axis

core/src/main/resources/hudson/model/Messages.properties

@@ -26,7 +26,7 @@ AbstractBuild.BuildingRemotely=Building remotely on {0}
 AbstractBuild.BuildingOnMaster=Building on master
 AbstractBuild_Building=Building
 AbstractBuild.BuildingInWorkspace=\ in workspace {0}
-AbstractBuild.KeptBecause=kept because of {0}
+AbstractBuild.KeptBecause=This build is kept because of {0}.
 
 AbstractItem.NoSuchJobExists=No such job ''{0}'' exists. Perhaps you meant ''{1}''?
 AbstractItem.Pronoun=Job
@@ -204,7 +204,7 @@ ResultTrend.StillUnstable=Still unstable
 ResultTrend.Success=Success
 ResultTrend.Unstable=Unstable
 Run.BuildAborted=Build was aborted
-Run.MarkedExplicitly=explicitly marked to keep the record
+Run.MarkedExplicitly=This record is explicitly marked to be kept.
 Run.Permissions.Title=Run
 Run.UnableToDelete=Unable to delete {0}: {1}
 Run.DeletePermission.Description=\

core/src/main/resources/hudson/model/Run/confirmDelete.properties

@@ -20,4 +20,4 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 # THE SOFTWARE.
 
-cannotMsg=Cannot delete this build, because it is {0}
\ No newline at end of file
+cannotMsg=Cannot delete this build: {0}