diff --git a/mercurial/configitems.py b/mercurial/configitems.py
--- a/mercurial/configitems.py
+++ b/mercurial/configitems.py
@@ -487,6 +487,9 @@
 coreconfigitem('experimental', 'evolution.bundle-obsmarker',
     default=False,
 )
+coreconfigitem('experimental', 'evolution.report-instabilities',
+    default=True,
+)
 coreconfigitem('experimental', 'evolution.track-operation',
     default=True,
 )
diff --git a/mercurial/scmutil.py b/mercurial/scmutil.py
--- a/mercurial/scmutil.py
+++ b/mercurial/scmutil.py
@@ -1260,7 +1260,8 @@
                 repo.ui.status(_('obsoleted %i changesets\n')
                                % len(obsoleted))
 
-    if obsolete.isenabled(repo, obsolete.createmarkersopt):
+    if (obsolete.isenabled(repo, obsolete.createmarkersopt) and
+        repo.ui.configbool('experimental', 'evolution.report-instabilities')):
         instabilitytypes = [
             ('orphan', 'orphan'),
             ('phase-divergent', 'phasedivergent'),
diff --git a/tests/test-obsolete.t b/tests/test-obsolete.t
--- a/tests/test-obsolete.t
+++ b/tests/test-obsolete.t
@@ -340,6 +340,17 @@
 
   $ cd ..
 
+Can disable transaction summary report
+
+  $ hg init transaction-summary
+  $ cd transaction-summary
+  $ mkcommit a
+  $ mkcommit b
+  $ hg up -q null
+  $ hg --config experimental.evolution.report-instabilities=false debugobsolete `getid a`
+  obsoleted 1 changesets
+  $ cd ..
+
 Exchange Test
 ============================