don't send spammy mentions

app/lib/activitypub/activity.rb

@@ -98,7 +98,7 @@ class ActivityPub::Activity
     crawl_links(status)
 
     notify_about_reblog(status) if reblog_of_local_account?(status) && !reblog_by_following_group_account?(status)
-    notify_about_mentions(status)
+    notify_about_mentions(status) unless spammy_mentions?(status)
 
     # Only continue if the status is supposed to have arrived in real-time.
     # Note that if @options[:override_timestamps] isn't set, the status
@@ -117,6 +117,11 @@ class ActivityPub::Activity
     status.reblog? && status.account.group? && status.reblog.account.following?(status.account)
   end
 
+  def spammy_mentions?(status)
+    status.has_non_mention_links? &&
+    @account.followers.local.count == 0
+  end
+
   def notify_about_reblog(status)
     NotifyService.new.call(status.reblog.account, :reblog, status)
   end

app/models/status.rb

@@ -351,6 +351,14 @@ class Status < ApplicationRecord
     super || build_status_stat
   end
 
+  def has_non_mention_links?
+    if local?
+      text.match? %r{https?://\w}
+    else
+      Nokogiri::HTML.fragment(text).css('a:not(.mention)').present?
+    end
+  end
+
   private
 
   def update_status_stat!(attrs)