diff --git a/backend/app/rest/api/rest_public.go b/backend/app/rest/api/rest_public.go
index c752256e..e91b5fbd 100644
--- a/backend/app/rest/api/rest_public.go
+++ b/backend/app/rest/api/rest_public.go
@@ -17,7 +17,7 @@ import (
 	"github.com/umputun/remark/backend/app/store"
 )
 
-// GET /find?site=siteID&url=post-url&format=[tree|plain]&sort=[+/-time|+/-score]
+// GET /find?site=siteID&url=post-url&format=[tree|plain]&sort=[+/-time|+/-score|+/-controversy ]
 // find comments for given post. Returns in tree or plain formats, sorted
 func (s *Rest) findCommentsCtrl(w http.ResponseWriter, r *http.Request) {
 	locator := store.Locator{SiteID: r.URL.Query().Get("site"), URL: r.URL.Query().Get("url")}
diff --git a/backend/app/rest/tree.go b/backend/app/rest/tree.go
index 58152217..5f439c63 100644
--- a/backend/app/rest/tree.go
+++ b/backend/app/rest/tree.go
@@ -151,6 +151,18 @@ func (t *Tree) sortNodes(sortType string) {
 			}
 			return t.Nodes[i].Comment.Score < t.Nodes[j].Comment.Score
 
+		case "+controversy", "-controversy", "controversy":
+			if strings.HasPrefix(sortType, "-") {
+				if t.Nodes[i].Comment.Controversy == t.Nodes[j].Comment.Controversy {
+					return t.Nodes[i].Comment.Timestamp.Before(t.Nodes[j].Comment.Timestamp)
+				}
+				return t.Nodes[i].Comment.Controversy > t.Nodes[j].Comment.Controversy
+			}
+			if t.Nodes[i].Comment.Controversy == t.Nodes[j].Comment.Controversy {
+				return t.Nodes[i].Comment.Timestamp.Before(t.Nodes[j].Comment.Timestamp)
+			}
+			return t.Nodes[i].Comment.Controversy < t.Nodes[j].Comment.Controversy
+
 		default:
 			return t.Nodes[i].Comment.Timestamp.Before(t.Nodes[j].Comment.Timestamp)
 		}
diff --git a/backend/app/rest/tree_test.go b/backend/app/rest/tree_test.go
index 114b533e..81daf834 100644
--- a/backend/app/rest/tree_test.go
+++ b/backend/app/rest/tree_test.go
@@ -96,15 +96,15 @@ func TestTreeSortNodes(t *testing.T) {
 	comments := []store.Comment{
 		{ID: "14", ParentID: "1", Timestamp: time.Date(2017, 12, 25, 19, 46, 14, 0, time.UTC)},
 		{ID: "132", ParentID: "13", Timestamp: time.Date(2017, 12, 25, 19, 46, 32, 0, time.UTC)},
-		{ID: "1", Timestamp: time.Date(2017, 12, 25, 19, 46, 1, 0, time.UTC), Score: 2},
-		{ID: "2", Timestamp: time.Date(2017, 12, 25, 19, 47, 2, 0, time.UTC), Score: 3},
+		{ID: "1", Timestamp: time.Date(2017, 12, 25, 19, 46, 1, 0, time.UTC), Score: 2, Controversy: 10},
+		{ID: "2", Timestamp: time.Date(2017, 12, 25, 19, 47, 2, 0, time.UTC), Score: 3, Controversy: 5},
 		{ID: "11", ParentID: "1", Timestamp: time.Date(2017, 12, 25, 19, 46, 11, 0, time.UTC)},
 		{ID: "13", ParentID: "1", Timestamp: time.Date(2017, 12, 25, 19, 46, 13, 0, time.UTC)},
 		{ID: "12", ParentID: "1", Timestamp: time.Date(2017, 12, 25, 19, 46, 14, 0, time.UTC)},
 		{ID: "131", ParentID: "13", Timestamp: time.Date(2017, 12, 25, 19, 50, 31, 0, time.UTC)},
 		{ID: "21", ParentID: "2", Timestamp: time.Date(2017, 12, 25, 19, 47, 21, 0, time.UTC)},
 		{ID: "22", ParentID: "2", Timestamp: time.Date(2017, 12, 25, 19, 47, 22, 0, time.UTC)},
-		{ID: "4", Timestamp: time.Date(2017, 12, 25, 19, 47, 22, 0, time.UTC), Score: -2},
+		{ID: "4", Timestamp: time.Date(2017, 12, 25, 19, 47, 22, 0, time.UTC), Score: -2, Controversy: 7},
 		{ID: "3", Timestamp: time.Date(2017, 12, 25, 19, 47, 22, 100, time.UTC)},
 		{ID: "6", Timestamp: time.Date(2017, 12, 25, 19, 47, 22, 200, time.UTC)},
 		{ID: "5", Deleted: true, Timestamp: time.Date(2017, 12, 25, 19, 47, 22, 150, time.UTC)},
@@ -140,6 +140,19 @@ func TestTreeSortNodes(t *testing.T) {
 	assert.Equal(t, "3", res.Nodes[2].Comment.ID)
 	assert.Equal(t, "6", res.Nodes[3].Comment.ID)
 
+	res = MakeTree(comments, "+controversy", 0)
+	assert.Equal(t, "3", res.Nodes[0].Comment.ID)
+	assert.Equal(t, "6", res.Nodes[1].Comment.ID)
+	assert.Equal(t, "2", res.Nodes[2].Comment.ID)
+	assert.Equal(t, "4", res.Nodes[3].Comment.ID)
+	assert.Equal(t, "1", res.Nodes[4].Comment.ID)
+
+	res = MakeTree(comments, "-controversy", 0)
+	assert.Equal(t, "1", res.Nodes[0].Comment.ID)
+	assert.Equal(t, "4", res.Nodes[1].Comment.ID)
+	assert.Equal(t, "2", res.Nodes[2].Comment.ID)
+	assert.Equal(t, "3", res.Nodes[3].Comment.ID)
+
 	res = MakeTree(comments, "undefined", 0)
 	t.Log(res.Nodes[0].Comment.ID, res.Nodes[0].tsModified)
 	assert.Equal(t, "1", res.Nodes[0].Comment.ID)
diff --git a/backend/app/store/engine/engine.go b/backend/app/store/engine/engine.go
index 7355a91c..b0e862b4 100644
--- a/backend/app/store/engine/engine.go
+++ b/backend/app/store/engine/engine.go
@@ -84,6 +84,18 @@ func sortComments(comments []store.Comment, sortFld string) []store.Comment {
 			}
 			return comments[i].Score < comments[j].Score
 
+		case "+controversy", "-controversy", "controversy":
+			if strings.HasPrefix(sortFld, "-") {
+				if comments[i].Controversy == comments[j].Controversy {
+					return comments[i].Timestamp.Before(comments[j].Timestamp)
+				}
+				return comments[i].Controversy > comments[j].Controversy
+			}
+			if comments[i].Controversy == comments[j].Controversy {
+				return comments[i].Timestamp.Before(comments[j].Timestamp)
+			}
+			return comments[i].Controversy < comments[j].Controversy
+
 		default:
 			return comments[i].Timestamp.Before(comments[j].Timestamp)
 		}
diff --git a/backend/app/store/engine/engine_test.go b/backend/app/store/engine/engine_test.go
index 68ef53d4..a17c35c4 100644
--- a/backend/app/store/engine/engine_test.go
+++ b/backend/app/store/engine/engine_test.go
@@ -11,10 +11,10 @@ import (
 
 func TestEngine_sortComments(t *testing.T) {
 	cc := []store.Comment{
-		{ID: "1", Score: 5, Timestamp: time.Date(2018, 2, 5, 10, 1, 0, 0, time.Local)},
-		{ID: "2", Score: 4, Timestamp: time.Date(2018, 2, 5, 10, 2, 0, 0, time.Local)},
-		{ID: "3", Score: 6, Timestamp: time.Date(2018, 2, 5, 10, 3, 0, 0, time.Local)},
-		{ID: "4", Score: 6, Timestamp: time.Date(2018, 2, 5, 10, 4, 0, 0, time.Local)},
+		{ID: "1", Score: 5, Controversy: 1, Timestamp: time.Date(2018, 2, 5, 10, 1, 0, 0, time.Local)},
+		{ID: "2", Score: 4, Controversy: 2, Timestamp: time.Date(2018, 2, 5, 10, 2, 0, 0, time.Local)},
+		{ID: "3", Score: 6, Controversy: 3, Timestamp: time.Date(2018, 2, 5, 10, 3, 0, 0, time.Local)},
+		{ID: "4", Score: 6, Controversy: 1, Timestamp: time.Date(2018, 2, 5, 10, 4, 0, 0, time.Local)},
 	}
 
 	sortComments(cc, "+time")
@@ -40,4 +40,16 @@ func TestEngine_sortComments(t *testing.T) {
 	assert.Equal(t, "4", cc[1].ID)
 	assert.Equal(t, "1", cc[2].ID)
 	assert.Equal(t, "2", cc[3].ID)
+
+	sortComments(cc, "controversy")
+	assert.Equal(t, "1", cc[0].ID)
+	assert.Equal(t, "4", cc[1].ID)
+	assert.Equal(t, "2", cc[2].ID)
+	assert.Equal(t, "3", cc[3].ID)
+
+	sortComments(cc, "-controversy")
+	assert.Equal(t, "3", cc[0].ID)
+	assert.Equal(t, "2", cc[1].ID)
+	assert.Equal(t, "1", cc[2].ID)
+	assert.Equal(t, "4", cc[3].ID)
 }