Joaquim Domingos António

If you wish to ‘Create comments’ using REST API, without exposing Administrator credentials to the Front-End application, you are at the right place. Since WordPress 4.7, REST API was natively included in WordPress.
In order to ‘Create a comment’ , the authentication for a user with ‘Administrator’ role is required. While this is a deliberately done for security reasons, such implementation makes it very hard for Front-End applications to implement a simple ‘Post Comment’ or ‘Reply Comment’ function.
This plugin fulfils such requirement by extending the existing WordPress REST API endpoints.
Requirements:
Minimum PHP version: 7.0 
Minimum WordPress version: 5.5
Installation:
Download the plugin form wordpress marketplace install it like any other WordPress plugin. 
After the installation activate the plugin through the ‘Plugins’ menu in WordPress
Endpoint:
When this plugin is installed one new endpoint is added to the wp/v2 namespace.
 Endpoint 
 HTTP Verb 
 Permalinks
 */wp-json/wp/v2/comments/create 
 POST 
 enabled
 */?rest_route=/wp/v2/comments/create 
 POST 
 disabled
Usage:
<ol>
<li>Create a Comment</li>
</ol>
To create a comment using REST API, send a <code>POST</code> request to:
<blockquote>
<code>/wp-json/wp/v2/comments/create</code> – if permalinks is enabled on your wordpress website.
</blockquote>
Or
<blockquote>
<code>/?rest_route=/wp/v2/comments/create</code> if permalinks is not enabled on your wordpress website.
</blockquote>
With a JSON body, as shown bellow:
<pre><code>`Json
</code></pre>
{ 
 “post”: “Post ID”, 
 “author_name”: “Comment Author’s name”, 
 “author_email”: “Comment Author’s email”, 
 “content”: “Comment content” 
} 
 `
The content may also be send as an object:
<pre><code>`Json
</code></pre>
{ 
 “post”: “Post ID”, 
 “author_name”: “Comment Author’s name”, 
 “author_email”: “Comment Author’s email”, 
 “content”: { 
 “raw”:”Comment content” 
 } 
} 
 `
Set header to:
<pre><code>`
</code></pre>
content-type: application/json 
 ` 
If successful, you should receive a response with the data of the created comment:
<pre><code>`Json
</code></pre>
{ 
 “id”: “[comment id]”, 
 “status”: “[comment status]”, 
 “message”:”[server response message]” 
} 
 `
In response header the status code should be:
<pre><code>`Http
</code></pre>
HTTP 201 Created 
 `
<ol>
<li>Reply a comment</li>
</ol>
To reply a comment you just need to add the field parent for the parent comment to the JSON body
<pre><code>`Json
</code></pre>
{ 
 “post”: “Post ID”, 
 “author_name”: “Comment Author’s name”, 
 “author_email”: “Comment Author’s email”, 
 “content”: “Comment content”, 
 “parent”:”Comment parent ID” 
} 
 `
<blockquote>
Note: Ensure the parent is a comment id that belongs to the post informed in the field post. The comment parent post id must match the post id otherwise the following error will be shown:
</blockquote>
<pre><code>`Json
</code></pre>
{ 
 “code”: “rest_post_mismatch_parent_post_id”, 
 “message”: “Post ID and Parent post ID does not match”, 
 “data”: { 
 “status”: 400 
 } 
} 
 `
<h3>Contact</h3>
If there is any thing to say about the plugin fill free to <a href="mailto:sopport@appsdabanda.com" rel="nofollow ugc">contact us</a>.

REST API Comment

REST API Comment adds in the 'Comment creation' function to the Wordpress REST API.

tstephenson

My use case is to allow content authors to write help pages in WordPress. 
This content is fetched and embedded into a single page application hosted on another domain.
AJAX requests to this site from another are typically disallowed by the browser’s security model. 
To permit legitimate uses the requesting browser may include an Origin header containing its domain. 
This plugin uses the Origin header to decide whether to allow the request or not. 
Allowed domains can be specified in the plugin’s Settings page.

WP-CORS

Allows AJAX requests from other sites to integrate content from your site using the CORS standard.

REST API Comment vs WP-CORS