another tweak

app/assets/javascripts/discourse/app/components/composer-editor.js

@@ -209,6 +209,8 @@ export default class ComposerEditor extends Component {
       this._throttledSyncEditorAndPreviewScroll
     );
 
+    input?.addEventListener("touchmove", this._textareaTouchMove);
+
     // Focus on the body unless we have a title
     if (!this.get("composer.model.canEditTitle")) {
       this.textManipulation.putCursorAtEnd();
@@ -219,6 +221,8 @@ export default class ComposerEditor extends Component {
         "scroll",
         this._throttledSyncEditorAndPreviewScroll
       );
+
+      input?.removeEventListener("touchmove", this._textareaTouchMove);
     };
   }
 
@@ -278,6 +282,18 @@ export default class ComposerEditor extends Component {
     );
   }
 
+  _textareaTouchMove(event) {
+    // TODO: should we limit this to mobile + ipad?
+    if (event.target) {
+      const notScrollable =
+        event.target.scrollHeight <= event.target.clientHeight;
+      if (notScrollable) {
+        event.preventDefault();
+        event.stopPropagation();
+      }
+    }
+  }
+
   _resetShouldBuildScrollMap() {
     this.set("shouldBuildScrollMap", true);
   }

app/assets/stylesheets/common/base/compose.scss

@@ -83,9 +83,7 @@ html.composer-open.not-mobile-device {
 
     .submit-panel,
     .composer-fields,
-    .d-editor-button-bar,
-    textarea:placeholder-shown {
-      // don't allow scrolling in the submit panel
+    .d-editor-button-bar {
       // this prevents bubbling to browser, i.e. accidental scrolls
       touch-action: none;
     }