fix

packages/svelte/src/internal/client/dom/blocks/each.js

@@ -637,7 +637,7 @@ function create_item(
 	try {
 		if (anchor === null) {
 			var fragment = document.createDocumentFragment();
-			fragment.append((anchor = document.createComment('')));
+			fragment.append((anchor = create_text()));
 		}
 
 		item.e = branch(() => render_fn(/** @type {Node} */ (anchor), v, i, get_collection), hydrating);

packages/svelte/src/internal/client/dom/blocks/if.js

@@ -12,7 +12,7 @@ import { block, branch, pause_effect, resume_effect } from '../../reactivity/eff
 import { HYDRATION_START_ELSE, UNINITIALIZED } from '../../../../constants.js';
 import { active_effect } from '../../runtime.js';
 import { add_boundary_callback, find_boundary } from './boundary.js';
-import { should_defer_append } from '../operations.js';
+import { create_text, should_defer_append } from '../operations.js';
 
 /**
  * @param {TemplateNode} node
@@ -115,7 +115,7 @@ export function if_block(node, fn, elseif = false) {
 
 		if (defer) {
 			offscreen_fragment = document.createDocumentFragment();
-			offscreen_fragment.append((target = document.createComment('')));
+			offscreen_fragment.append((target = create_text()));
 		}
 
 		if (condition ? !consequent_effect : !alternate_effect) {
@@ -124,6 +124,7 @@ export function if_block(node, fn, elseif = false) {
 
 		if (defer) {
 			add_boundary_callback(boundary, commit);
+			target.remove();
 		} else {
 			commit();
 		}

packages/svelte/src/internal/client/dom/blocks/key.js

@@ -6,7 +6,7 @@ import { active_effect } from '../../runtime.js';
 import { is_runes } from '../../context.js';
 import { hydrate_next, hydrate_node, hydrating } from '../hydration.js';
 import { add_boundary_callback, find_boundary } from './boundary.js';
-import { should_defer_append } from '../operations.js';
+import { create_text, should_defer_append } from '../operations.js';
 
 /**
  * @template V
@@ -62,13 +62,14 @@ export function key_block(node, get_key, render_fn) {
 
 			if (defer) {
 				offscreen_fragment = document.createDocumentFragment();
-				offscreen_fragment.append((target = document.createComment('')));
+				offscreen_fragment.append((target = create_text()));
 			}
 
 			pending_effect = branch(() => render_fn(target));
 
 			if (defer) {
 				add_boundary_callback(boundary, commit);
+				target.remove();
 			} else {
 				commit();
 			}

packages/svelte/src/internal/client/dom/blocks/svelte-component.js

@@ -3,7 +3,7 @@ import { EFFECT_TRANSPARENT } from '../../constants.js';
 import { block, branch, pause_effect } from '../../reactivity/effects.js';
 import { active_effect } from '../../runtime.js';
 import { hydrate_next, hydrate_node, hydrating } from '../hydration.js';
-import { should_defer_append } from '../operations.js';
+import { create_text, should_defer_append } from '../operations.js';
 import { add_boundary_callback, find_boundary } from './boundary.js';
 
 /**
@@ -59,10 +59,14 @@ export function component(node, get_component, render_fn) {
 
 			if (defer) {
 				offscreen_fragment = document.createDocumentFragment();
-				offscreen_fragment.append((target = document.createComment('')));
+				offscreen_fragment.append((target = create_text()));
 			}
 
 			pending_effect = branch(() => render_fn(target, component));
+
+			if (defer) {
+				target.remove();
+			}
 		}
 
 		if (defer) {