diff --git a/source/blender/blenkernel/intern/mesh.c b/source/blender/blenkernel/intern/mesh.c
index 3717a9eb22a..6a0c0c14a23 100644
--- a/source/blender/blenkernel/intern/mesh.c
+++ b/source/blender/blenkernel/intern/mesh.c
@@ -1395,9 +1395,7 @@ void BKE_mesh_from_nurbs_displist(Object *ob, ListBase *dispbase, const bool use
 	cu->mat = NULL;
 	cu->totcol = 0;
 
-	if (ob->data) {
-		BKE_libblock_free(bmain, ob->data);
-	}
+	/* Do not decrement ob->data usercount here, it's done at end of func with BKE_libblock_free_us() call. */
 	ob->data = me;
 	ob->type = OB_MESH;
 
@@ -1407,11 +1405,14 @@ void BKE_mesh_from_nurbs_displist(Object *ob, ListBase *dispbase, const bool use
 		if (ob1->data == cu) {
 			ob1->type = OB_MESH;
 		
+			id_us_min((ID *)ob1->data);
 			ob1->data = ob->data;
-			id_us_plus((ID *)ob->data);
+			id_us_plus((ID *)ob1->data);
 		}
 		ob1 = ob1->id.next;
 	}
+
+	BKE_libblock_free_us(bmain, cu);
 }
 
 void BKE_mesh_from_nurbs(Object *ob)
diff --git a/source/blender/blenkernel/intern/sequencer.c b/source/blender/blenkernel/intern/sequencer.c
index 0d7a374a446..e316b7f26e9 100644
--- a/source/blender/blenkernel/intern/sequencer.c
+++ b/source/blender/blenkernel/intern/sequencer.c
@@ -5185,6 +5185,7 @@ Sequence *BKE_sequencer_add_sound_strip(bContext *C, ListBase *seqbasep, SeqLoad
 	sound = BKE_sound_new_file(bmain, seq_load->path); /* handles relative paths */
 
 	if (sound->playback_handle == NULL) {
+		BKE_libblock_free(bmain, sound);
 #if 0
 		if (op)
 			BKE_report(op->reports, RPT_ERROR, "Unsupported audio format");
diff --git a/source/blender/blenloader/intern/versioning_defaults.c b/source/blender/blenloader/intern/versioning_defaults.c
index 002af20bc3a..50f96a6d438 100644
--- a/source/blender/blenloader/intern/versioning_defaults.c
+++ b/source/blender/blenloader/intern/versioning_defaults.c
@@ -271,13 +271,13 @@ void BLO_update_defaults_startup_blend(Main *bmain)
 		/* remove polish brush (flatten/contrast does the same) */
 		br = (Brush *)BKE_libblock_find_name_ex(bmain, ID_BR, "Polish");
 		if (br) {
-			BKE_libblock_free(bmain, br);
+			BKE_libblock_delete(bmain, br);
 		}
 
 		/* remove brush brush (huh?) from some modes (draw brushes do the same) */
 		br = (Brush *)BKE_libblock_find_name_ex(bmain, ID_BR, "Brush");
 		if (br) {
-			BKE_libblock_free(bmain, br);
+			BKE_libblock_delete(bmain, br);
 		}
 
 		/* remove draw brush from texpaint (draw brushes do the same) */
diff --git a/source/blender/collada/DocumentImporter.cpp b/source/blender/collada/DocumentImporter.cpp
index 7cb6045b73e..2d428d6fe5d 100644
--- a/source/blender/collada/DocumentImporter.cpp
+++ b/source/blender/collada/DocumentImporter.cpp
@@ -391,9 +391,7 @@ Object *DocumentImporter::create_camera_object(COLLADAFW::InstanceCamera *camera
 	Camera *cam = uid_camera_map[cam_uid];
 	Camera *old_cam = (Camera *)ob->data;
 	ob->data = cam;
-	id_us_min(&old_cam->id);
-	if (old_cam->id.us == 0)
-		BKE_libblock_free(G.main, old_cam);
+	BKE_libblock_free_us(G.main, old_cam);
 	return ob;
 }
 
@@ -409,9 +407,7 @@ Object *DocumentImporter::create_lamp_object(COLLADAFW::InstanceLight *lamp, Sce
 	Lamp *la = uid_lamp_map[lamp_uid];
 	Lamp *old_lamp = (Lamp *)ob->data;
 	ob->data = la;
-	id_us_min(&old_lamp->id);
-	if (old_lamp->id.us == 0)
-		BKE_libblock_free(G.main, old_lamp);
+	BKE_libblock_free_us(G.main, old_lamp);
 	return ob;
 }
 
diff --git a/source/blender/collada/MeshImporter.cpp b/source/blender/collada/MeshImporter.cpp
index 616c254a6ea..9c95d4de695 100644
--- a/source/blender/collada/MeshImporter.cpp
+++ b/source/blender/collada/MeshImporter.cpp
@@ -1156,8 +1156,9 @@ Object *MeshImporter::create_mesh_object(COLLADAFW::Node *node, COLLADAFW::Insta
 	BKE_mesh_assign_object(ob, new_mesh);
 	BKE_mesh_calc_normals(new_mesh);
 
-	if (old_mesh->id.us == 0) BKE_libblock_free(G.main, old_mesh);
-	
+	id_us_plus(&old_mesh->id);  /* Because BKE_mesh_assign_object would have already decreased it... */
+	BKE_libblock_free_us(G.main, old_mesh);
+
 	COLLADAFW::MaterialBindingArray& mat_array =
 	    geom->getMaterialBindings();
 	
diff --git a/source/blender/editors/object/object_add.c b/source/blender/editors/object/object_add.c
index 33af8f94d04..e8343dce384 100644
--- a/source/blender/editors/object/object_add.c
+++ b/source/blender/editors/object/object_add.c
@@ -1701,7 +1701,7 @@ static int convert_exec(bContext *C, wmOperator *op)
 	MetaBall *mb;
 	Mesh *me;
 	const short target = RNA_enum_get(op->ptr, "target");
-	const bool keep_original = RNA_boolean_get(op->ptr, "keep_original");
+	bool keep_original = RNA_boolean_get(op->ptr, "keep_original");
 	int a, mballConverted = 0;
 
 	/* don't forget multiple users! */
@@ -1738,7 +1738,20 @@ static int convert_exec(bContext *C, wmOperator *op)
 	 * on other objects data masks too, see: T50950. */
 	{
 		for (CollectionPointerLink *link = selected_editable_bases.first; link; link = link->next) {
-			Base *base = link->ptr.data;
+			BaseLegacy *base = link->ptr.data;
+			ob = base->object;
+
+			/* The way object type conversion works currently (enforcing conversion of *all* objetcs using converted
+			 * obdata, even some un-selected/hidden/inother scene ones, sounds totally bad to me.
+			 * However, changing this is more design than bugfix, not to mention convoluted code below,
+			 * so that will be for later.
+			 * But at the very least, do not do that with linked IDs! */
+			if ((ID_IS_LINKED_DATABLOCK(ob) || ID_IS_LINKED_DATABLOCK(ob->data)) && !keep_original) {
+				keep_original = true;
+				BKE_reportf(op->reports, RPT_INFO,
+				            "Converting some linked object/object data, enforcing 'Keep Original' option to True");
+			}
+
 			DEG_id_tag_update(&base->object->id, OB_RECALC_DATA);
 		}
 
@@ -1749,7 +1762,7 @@ static int convert_exec(bContext *C, wmOperator *op)
 	}
 
 	for (CollectionPointerLink *link = selected_editable_bases.first; link; link = link->next) {
-		Base *base = link->ptr.data;
+		BaseLegacy *base = link->ptr.data;
 		ob = base->object;
 
 		if (ob->flag & OB_DONE || !IS_TAGGED(ob->data)) {
diff --git a/source/blender/editors/object/object_group.c b/source/blender/editors/object/object_group.c
index 9d06624bd9c..3064bf8af1a 100644
--- a/source/blender/editors/object/object_group.c
+++ b/source/blender/editors/object/object_group.c
@@ -522,8 +522,7 @@ static int group_unlink_exec(bContext *C, wmOperator *UNUSED(op))
 	if (!group)
 		return OPERATOR_CANCELLED;
 
-	BKE_libblock_unlink(bmain, group, false, false);
-	BKE_libblock_free(bmain, group);
+	BKE_libblock_delete(bmain, group);
 
 	WM_event_add_notifier(C, NC_OBJECT | ND_DRAW, NULL);
 
diff --git a/source/blender/editors/space_outliner/outliner_tools.c b/source/blender/editors/space_outliner/outliner_tools.c
index 9ada1243c49..f2d73f40039 100644
--- a/source/blender/editors/space_outliner/outliner_tools.c
+++ b/source/blender/editors/space_outliner/outliner_tools.c
@@ -239,8 +239,7 @@ static void unlink_group_cb(
 	}
 	else {
 		Main *bmain = CTX_data_main(C);
-		BKE_libblock_unlink(bmain, group, false, false);
-		BKE_libblock_free(bmain, group);
+		BKE_libblock_delete(bmain, group);
 	}
 }