Ensure ampify_threaded_comments runs when in Strict sandboxing

[westonruter]

Summary

Fixes #6443 (comment).

As discovered by @milindmore22, when a site is in the Strict level for Sandboxing, the ampification of threaded comments was failing to happen. This meant that the comment form lacked the expected on="submit-success:commentform.clear,AMP.setState({ampCommentThreading: {"replyTo":"","commentParent":"0"}})" attribute, and amp-bind was not being used for comment replies.

The issue is that in Strict mode, the script sanitizer will remove all scripts, including the comment-reply one:

amp-wp/includes/sanitizers/class-amp-script-sanitizer.php

Line 60 in 4558144

'comment_reply_allowed' => 'never', // Can be 'never' , 'always', or 'conditionally'.

amp-wp/includes/sanitizers/class-amp-script-sanitizer.php

Lines 348 to 358 in 4558144

	// Handle the comment-reply script, removing it if it's not never allowed, marking it as PX-verified if it is
	// always allowed, or leaving it alone if it is 'conditionally' allowed since it will be dealt with later
	// in the AMP_Comments_Sanitizer.
	if ( $comment_reply_script ) {
	if ( 'never' === $this->args['comment_reply_allowed'] ) {
	$comment_reply_script->parentNode->removeChild( $comment_reply_script );
	} elseif ( 'always' === $this->args['comment_reply_allowed'] ) {
	// Prevent the comment-reply script from being removed later in the comments sanitizer.
	ValidationExemption::mark_node_as_px_verified( $comment_reply_script );
	}
	}

However, the comments sanitizer was using the presence of this script to determine whether to ampify commenting:

amp-wp/includes/sanitizers/class-amp-comments-sanitizer.php

Lines 78 to 80 in 4558144

	$comment_reply_script = $this->get_comment_reply_script();
	$should_ampify_comment_threading = false;
	if ( $comment_reply_script instanceof Element ) {

So we just need to replace the false with a 'always' === $this->args['ampify_comment_threading'] condition so that even when the script is not on the page, the ampification will be done.

Checklist

• My code is tested and passes existing tests.
• My code follows the Engineering Guidelines (updates are often made to the guidelines, check it out periodically).

[github-actions]

Plugin builds for ce54a32 are ready 🛎️!

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[westonruter]

Please code review as part of QA.

[milindmore22]

QA Passed
The fix resolved comment box not having on attribute in Sandboxing level Strict, Other Sandboxing levels, Moderate and loose also Looks good 👍🏼