A WordPress plugin, SMS Twilio Comment Notifier, allows users to receive text messages when someone replies to their comment. The plugin uses Twilio's API to send and receive SMS notifications. When a user replies to a comment, the plugin checks if it's a reply to another comment. If it is, it sends an SMS notification to the original commenter with a link to the commented post. Users can enter their mobile number on their profile screen to receive these notifications. The plugin also allows users to reply to comments by texting a specific format. When a user replies, the plugin extracts the post ID from the text and posts a comment using the WordPress REST API. If there's an error posting the comment, the plugin returns an error; otherwise, it returns a success response.