Fix code review comments

lib/comment_tree.dart

@@ -5,7 +5,6 @@ import 'util/hot_rank.dart';
 enum CommentSortType {
   hot,
   top,
-  // ignore: constant_identifier_names
   new_,
   old,
   chat,

lib/pages/create_post/create_post_community_picker.dart

@@ -32,7 +32,8 @@ class CreatePostCommunityPicker extends HookWidget {
             controller.text = '';
           }
         },
-        child: TypeAheadFormField<CommunityView>(
+        child: ObserverBuilder<CreatePostStore>(builder: (context, store) {
+          return TypeAheadFormField<CommunityView>(
             textFieldConfiguration: TextFieldConfiguration(
               controller: controller,
               enabled: !store.isEdit,
@@ -42,7 +43,15 @@ class CreatePostCommunityPicker extends HookWidget {
                   vertical: 16,
                   horizontal: 20,
                 ),
-              suffixIcon: const Icon(Icons.arrow_drop_down),
+                suffixIcon: store.selectedCommunity == null
+                    ? const Icon(Icons.arrow_drop_down)
+                    : IconButton(
+                        onPressed: () {
+                          store.selectedCommunity = null;
+                          controller.clear();
+                        },
+                        icon: const Icon(Icons.close),
+                      ),
               ),
               onChanged: (_) => store.selectedCommunity = null,
             ),
@@ -88,7 +97,8 @@ class CreatePostCommunityPicker extends HookWidget {
               ],
             ),
             debounceDuration: const Duration(milliseconds: 400),
-        ),
+          );
+        }),
       ),
     );
   }

lib/pages/create_post/create_post_store.dart

@@ -59,7 +59,7 @@ abstract class _CreatePostStore with Store {
         ListCommunities(
           type: PostListingType.all,
           sort: SortType.topAll,
-          limit: 20,
+          limit: 10,
           auth: token?.raw,
         ),
       );
@@ -70,7 +70,7 @@ abstract class _CreatePostStore with Store {
           q: searchTerm,
           sort: SortType.topAll,
           listingType: PostListingType.all,
-          limit: 20,
+          limit: 10,
           auth: token?.raw,
         ),
       );

lib/pages/create_post/create_post_url_field.dart

@@ -34,7 +34,7 @@ class CreatePostUrlField extends HookWidget {
 
     return ObserverConsumer<CreatePostStore>(
       listener: (context, store) {
-        // needed since flutter's TextFields cannot work as dumb widgets
+        // needed to keep the controller and store data in sync
         if (controller.text != store.url) {
           controller.text = store.url;
         }