diff --git a/lib/shared/messages/add-members-message-spec.js b/lib/shared/messages/add-members-message-spec.js
--- a/lib/shared/messages/add-members-message-spec.js
+++ b/lib/shared/messages/add-members-message-spec.js
@@ -7,6 +7,7 @@
   MessageSpec,
   NotificationTextsParams,
   MergeRobotextMessageItemResult,
+  ShowInMessagePreviewParams,
 } from './message-spec.js';
 import { joinResult } from './utils.js';
 import type { RobotextChatMessageInfoItem } from '../../selectors/chat-selectors.js';
@@ -23,6 +24,7 @@
 } from '../../types/messages/add-members.js';
 import type { ThreadInfo } from '../../types/minimally-encoded-thread-permissions-types.js';
 import type { NotifTexts } from '../../types/notif-types.js';
+import { threadTypeIsThick } from '../../types/thread-types-enum.js';
 import type { RelativeUserInfo } from '../../types/user-types.js';
 import {
   type EntityText,
@@ -224,4 +226,9 @@
     };
     return { shouldMerge: true, item: mergedItem };
   },
+
+  showInMessagePreview: async (
+    messageInfo: AddMembersMessageInfo,
+    params: ShowInMessagePreviewParams,
+  ) => threadTypeIsThick(params.threadInfo.type),
 });
diff --git a/lib/shared/messages/join-thread-message-spec.js b/lib/shared/messages/join-thread-message-spec.js
--- a/lib/shared/messages/join-thread-message-spec.js
+++ b/lib/shared/messages/join-thread-message-spec.js
@@ -6,6 +6,7 @@
   MessageSpec,
   RobotextParams,
   MergeRobotextMessageItemResult,
+  ShowInMessagePreviewParams,
 } from './message-spec.js';
 import { joinResult } from './utils.js';
 import type { RobotextChatMessageInfoItem } from '../../selectors/chat-selectors.js';
@@ -22,6 +23,7 @@
 } from '../../types/messages/join-thread.js';
 import type { ThreadInfo } from '../../types/minimally-encoded-thread-permissions-types.js';
 import type { NotifTexts } from '../../types/notif-types.js';
+import { threadTypeIsThick } from '../../types/thread-types-enum.js';
 import type { RelativeUserInfo } from '../../types/user-types.js';
 import {
   type EntityText,
@@ -170,4 +172,9 @@
     };
     return { shouldMerge: true, item: mergedItem };
   },
+
+  showInMessagePreview: async (
+    messageInfo: JoinThreadMessageInfo,
+    params: ShowInMessagePreviewParams,
+  ) => threadTypeIsThick(params.threadInfo.type),
 });
diff --git a/lib/shared/messages/leave-thread-message-spec.js b/lib/shared/messages/leave-thread-message-spec.js
--- a/lib/shared/messages/leave-thread-message-spec.js
+++ b/lib/shared/messages/leave-thread-message-spec.js
@@ -6,6 +6,7 @@
   MessageSpec,
   RobotextParams,
   MergeRobotextMessageItemResult,
+  ShowInMessagePreviewParams,
 } from './message-spec.js';
 import { joinResult } from './utils.js';
 import type { RobotextChatMessageInfoItem } from '../../selectors/chat-selectors.js';
@@ -22,6 +23,7 @@
 } from '../../types/messages/leave-thread.js';
 import type { ThreadInfo } from '../../types/minimally-encoded-thread-permissions-types.js';
 import type { NotifTexts } from '../../types/notif-types.js';
+import { threadTypeIsThick } from '../../types/thread-types-enum.js';
 import type { RelativeUserInfo } from '../../types/user-types.js';
 import {
   type EntityText,
@@ -170,4 +172,9 @@
     };
     return { shouldMerge: true, item: mergedItem };
   },
+
+  showInMessagePreview: async (
+    messageInfo: LeaveThreadMessageInfo,
+    params: ShowInMessagePreviewParams,
+  ) => threadTypeIsThick(params.threadInfo.type),
 });
diff --git a/lib/shared/messages/remove-members-message-spec.js b/lib/shared/messages/remove-members-message-spec.js
--- a/lib/shared/messages/remove-members-message-spec.js
+++ b/lib/shared/messages/remove-members-message-spec.js
@@ -7,6 +7,7 @@
   MessageSpec,
   NotificationTextsParams,
   MergeRobotextMessageItemResult,
+  ShowInMessagePreviewParams,
 } from './message-spec.js';
 import { joinResult } from './utils.js';
 import type { RobotextChatMessageInfoItem } from '../../selectors/chat-selectors.js';
@@ -23,6 +24,7 @@
 } from '../../types/messages/remove-members.js';
 import type { ThreadInfo } from '../../types/minimally-encoded-thread-permissions-types.js';
 import type { NotifTexts } from '../../types/notif-types.js';
+import { threadTypeIsThick } from '../../types/thread-types-enum.js';
 import type { RelativeUserInfo } from '../../types/user-types.js';
 import {
   type EntityText,
@@ -230,5 +232,10 @@
       };
       return { shouldMerge: true, item: mergedItem };
     },
+
+    showInMessagePreview: async (
+      messageInfo: RemoveMembersMessageInfo,
+      params: ShowInMessagePreviewParams,
+    ) => threadTypeIsThick(params.threadInfo.type),
   },
 );