Add a comment and remove the toggle

packages/block-library/src/post-featured-image/edit.js

@@ -209,16 +209,6 @@ export default function PostFeaturedImageEdit( {
 							/>
 						</>
 					) }
-					<ToggleControl
-						__nextHasNoMarginBottom
-						label={ __( 'Use first image from post' ) }
-						onChange={ ( value ) =>
-							setAttributes( {
-								useFirstImageFromPost: value,
-							} )
-						}
-						checked={ useFirstImageFromPost }
-					/>
 				</PanelBody>
 			</InspectorControls>
 		</>

packages/block-library/src/post-featured-image/index.php

@@ -60,6 +60,19 @@ function render_block_core_post_featured_image( $attributes, $content, $block )
 		$content_post = get_post( $post_ID );
 		$content = $content_post->post_content;
 		$processor = new WP_HTML_Tag_Processor( $content );
+		/*
+		 * Transfer the image tag from the post into a new text snippet.
+		 * Because the HTML API doesn't currently expose a way to extract
+		 * HTML substrings this is necessary as a workaround. Of note, this
+		 * is different than directly extracting the IMG tag:
+		 * - If there are duplicate attributes in the source there will only be one in the output.
+		 * - If there are single-quoted or unquoted attributes they will be double-quoted in the output.
+		 * - If there are named character references in the attribute values they may be replaced with their direct code points. E.g. `…` becomes `…`.
+		 * In the future there will likely be a mechanism to copy snippets of HTML from
+		 * one document into another, via the HTML Processor's `get_outer_html()` or
+		 * equivalent. When that happens it would be appropriate to replace this custom
+		 * code with that canonical code.
+		 */
 		if ( $processor->next_tag( 'img' ) ) {
 			$tag_html = new WP_HTML_Tag_Processor( '<img>' );
 			$tag_html->next_tag();