diff --git a/script/fixes/126_import_post_replacements_from_comments.rb b/script/fixes/126_import_post_replacements_from_comments.rb
new file mode 100755
index 000000000..c46b43da4
--- /dev/null
+++ b/script/fixes/126_import_post_replacements_from_comments.rb
@@ -0,0 +1,137 @@
+#!/usr/bin/env ruby
+
+require_relative "base"
+
+CurrentUser.user = User.system
+
+# Parse the data from a DanbooruBot replacement comment.
+def parse_comment(comment)
+  dtext = DText.format_text(comment.body)
+  html = Nokogiri::HTML5.fragment(dtext)
+
+  old_source = html.css("table tr:first-child td a")[0]&.get_attribute("href") || html.css("table tr:first-child td")[0].text
+  old_md5 = html.css("table tr:first-child td")[1].text
+  old_file_ext = html.css("table tr:first-child td")[2].text
+  old_image_width, old_image_height = html.css("table tr:first-child td")[3].text.split(" x ").map(&:to_i)
+  old_file_size = html.css("table tr:first-child td")[4].text
+
+  new_source = html.css("table tr:last-child td a")[0]&.get_attribute("href") || html.css("table tr:last-child td")[0].text
+  new_md5 = html.css("table tr:last-child td")[1].text
+  new_file_ext = html.css("table tr:last-child td")[2].text
+  new_image_width, new_image_height = html.css("table tr:last-child td")[3].text.split(" x ").map(&:to_i)
+  new_file_size = html.css("table tr:last-child td")[4].text
+
+  replacer_name = html.css("a.dtext-user-mention-link")[0]&.get_attribute("data-user-name")
+  replacer_name = "user_166417" if replacer_name == "Randeel"
+
+  if replacer_name.nil?
+    replacer_id = html.css("a.dtext-link[href^='/users']")[0]["href"][%r{^/users/([0-9]+)$}, 1]
+    replacer = User.find(replacer_id)
+  else
+    replacer = User.find_by_name(replacer_name) || UserNameChangeRequest.find_by(original_name: replacer_name)&.user
+  end
+
+  raise "unknown replacer" if replacer.nil?
+
+  OpenStruct.new(
+    old_source:, old_md5:, old_file_ext:, old_file_size:, old_image_width:, old_image_height:,
+    new_source:, new_md5:, new_file_ext:, new_file_size:, new_image_width:, new_image_height:,
+    replacer:
+  )
+end
+
+# Given a post, pair each replacement with the matching comment. Some replacements may not have a matching comment. This
+# can happen because replacements that didn't change the MD5 didn't leave comments. Return the replacement-comment pairs
+# and the leftover replacements.
+def pair_comments(post)
+  replacements = post.replacements.order(id: :asc).to_a
+  comments = post.comments.where(creator: User.system).where_regex(:body, "replaced this post").order(id: :asc).to_a
+  pairs = []
+
+  while replacements.present? && comments.present?
+    # Take the Cartesian product of all possible replacement-comment pairs, filter for matching pairs, and take the pair
+    # with the closest matching created_at times.
+    replacement, comment = replacements.product(comments).select do |replacement, comment|
+      data = parse_comment(comment)
+
+      if replacement.old_md5.present? && replacement.md5.present?
+        data.old_source == replacement.original_url && data.replacer == replacement.creator && data.old_md5 == replacement.old_md5 && data.new_md5 == replacement.md5
+      elsif replacement.old_md5.present?
+        data.old_source == replacement.original_url && data.replacer == replacement.creator && data.old_md5 == replacement.old_md5
+      else
+        data.old_source == replacement.original_url && data.replacer == replacement.creator
+      end
+    end.min_by do |replacement, comment|
+      [(replacement.updated_at - comment.created_at).abs, replacement.id, comment.id]
+    end
+
+    pairs << [replacement, comment]
+    replacements -= [replacement]
+    comments -= [comment]
+  end
+
+  [pairs, replacements]
+end
+
+with_confirmation do
+  fix = ENV.fetch("FIX", "false").truthy?
+  cond = ENV.fetch("COND", "TRUE")
+
+  post_ids = PostReplacement.where(md5: nil).or(PostReplacement.where(old_md5: nil)).where(cond).pluck(:post_id).sort.uniq
+
+  post_ids.each do |post_id|
+    post = Post.find(post_id)
+    replacements = post.replacements
+    comments = post.comments.where(creator: User.system).where_regex(:body, "replaced this post")
+
+    pairs, leftover_replacements = pair_comments(post)
+
+    leftover_replacements.each do |replacement|
+      #puts ({ error: "couldn't find comment", post: post.id, replacement: replacement.id, replacements: replacements.size, comments: comments.size, replacer: replacement.creator.name, old_md5: replacement.old_md5, new_md5: replacement.md5 }.to_json)
+    end
+
+    pairs.each do |replacement, comment|
+      data = parse_comment(comment)
+      replacer = data.replacer
+
+      if replacer != replacement.creator
+        puts ({ error: "replacer/replacement creator mismatch", post: post.id, replacement: replacement.id, comment: comment.id, replacements: replacements.size, comments: comments.size, timediff: (comment.created_at - replacement.updated_at).abs.to_i, replacer: replacement.creator.name, }.to_json)
+        next
+      end
+
+      #if replacer != comment.updater && !comment.is_deleted?
+      #  puts ({ error: "replacer/comment updater mismatch", post: post.id, replacement: replacement.id, comment: comment.id, replacements: replacements.size, comments: comments.size, timediff: (comment.created_at - replacement.updated_at).abs.to_i, replacer: replacement.creator.name, updater: comment.updater.name }.to_json)
+      #  next
+      #end
+
+      if (replacement.updated_at - comment.created_at).abs > 70.seconds
+        puts ({ error: "timestamp mismatch", post: post.id, replacement: replacement.id, comment: comment.id, replacements: replacements.size, comments: comments.size, timediff: (comment.created_at - replacement.updated_at).abs.to_i, replacer: replacement.creator.name, }.to_json)
+        next
+      end
+
+      if data.old_source.to_s != replacement.original_url
+        puts ({ error: "old source mismatch", post: post.id, replacement: replacement.id, comment: comment.id, replacements: replacements.size, comments: comments.size, timediff: (comment.created_at - replacement.updated_at).abs.to_i, replacer: replacement.creator.name, comment_old_source: data.old_source, replacement_old_source: replacement.original_url }.to_json)
+        next
+      end
+
+      #if data.new_source != replacement.replacement_url.strip
+      #  puts ({ error: "new source mismatch", post: post.id, replacement: replacement.id, comment: comment.id, replacements: replacements.size, comments: comments.size, timediff: (comment.created_at - replacement.updated_at).abs.to_i, replacer: replacement.creator.name, comment_new_source: data.new_source, replacement_new_source: replacement.replacement_url }.to_json)
+      #  next
+      #end
+
+      replacement.old_md5 = data.old_md5 if replacement.old_md5.blank?
+      replacement.md5 = data.new_md5 if replacement.md5.blank?
+
+      puts ({ post: post.id, replacement: replacement.id, comment: comment.id, replacements: replacements.size, comments: comments.size, timediff: (comment.created_at - replacement.updated_at).abs.to_i, replacer: replacement.creator.name, replacement_changes: replacement.changes }.to_json)
+
+      if replacement.changed? && fix
+        replacement.save!(touch: false)
+      end
+    end
+  end
+
+  comments = User.system.comments.undeleted.where_regex(:body, "replaced this post").find_each do |comment|
+    comment.update!(is_deleted: true) if fix
+    puts "deleted comment ##{comment.id}"
+  end
+end