Minor comments about current usages of `BKE_main_namemap_destroy`.

source/blender/blenkernel/intern/blendfile.cc

@@ -214,6 +214,8 @@ static void setup_app_data(bContext *C,
     SWAP(ListBase, bmain->wm, bfd->main->wm);
     SWAP(ListBase, bmain->workspaces, bfd->main->workspaces);
     SWAP(ListBase, bmain->screens, bfd->main->screens);
+    /* NOTE: UI IDs are assumed to be only local data-blocks, so no need to call
+     * #BKE_main_namemap_clear here (otherwise, the swapping would fail in many funny ways). */
     if (bmain->name_map != nullptr) {
       BKE_main_namemap_destroy(&bmain->name_map);
     }

source/blender/blenkernel/intern/main.c

@@ -186,6 +186,7 @@ void BKE_main_free(Main *mainvar)
     BKE_main_idmap_destroy(mainvar->id_map);
   }
 
+  /* NOTE: `name_map` in libraries are freed together with the library IDs above. */
   if (mainvar->name_map) {
     BKE_main_namemap_destroy(&mainvar->name_map);
   }

source/blender/windowmanager/intern/wm_files.cc

@@ -207,6 +207,8 @@ static void wm_window_match_init(bContext *C, ListBase *wmlist)
 
   BLI_listbase_clear(&G_MAIN->wm);
   if (G_MAIN->name_map != nullptr) {
+    /* NOTE: UI IDs are assumed to be only local data-blocks, so no need to call
+     * #BKE_main_namemap_clear here. */
     BKE_main_namemap_destroy(&G_MAIN->name_map);
   }