New users can only post newuser_max_replies_per_topic times per topic.

lib/composer_messages_finder.rb

@@ -7,6 +7,7 @@ class ComposerMessagesFinder
 
   def find
     check_education_message ||
+    check_new_user_many_replies ||
     check_avatar_notification ||
     check_sequential_replies ||
     check_dominating_topic
@@ -32,6 +33,12 @@ class ComposerMessagesFinder
     nil
   end
 
+  # New users have a limited number of replies in a topic
+  def check_new_user_many_replies
+    return unless replying? && @user.posted_too_much_in_topic?(@details[:topic_id])
+    {templateName: 'composer/education', body: PrettyText.cook(I18n.t('education.too_many_replies', newuser_max_replies_per_topic: SiteSetting.newuser_max_replies_per_topic)) }
+  end
+
   # Should a user be contacted to update their avatar?
   def check_avatar_notification
 

lib/validators/post_validator.rb

@@ -5,6 +5,7 @@ class Validators::PostValidator < ActiveModel::Validator
     presence(record)
     stripped_length(record)
     raw_quality(record)
+    max_posts_validator(record)
     max_mention_validator(record)
     max_images_validator(record)
     max_attachments_validator(record)
@@ -40,6 +41,12 @@ class Validators::PostValidator < ActiveModel::Validator
     end
   end
 
+  def max_posts_validator(post)
+    if post.acting_user.present? && post.acting_user.posted_too_much_in_topic?(post.topic_id)
+      post.errors.add(:base, I18n.t(:too_many_replies))
+    end
+  end
+
   # Ensure new users can not put too many images in a post
   def max_images_validator(post)
     add_error_if_count_exceeded(post, :too_many_images, post.image_count, SiteSetting.newuser_max_images) unless acting_user_is_trusted?(post)