Explain why substack.com is blocked

Source/domainset/reject.conf

@@ -426,10 +426,30 @@ inst.360safe.com
 # Notorious Bulk Phishing/Spam Email Sender
 .sephora.com
 .tiscali.it
-.substack.com
 .smallstep.org
 .gop.com
 
+# substack is notiorious for bad platform abuse. they allow anyone to
+# send phishing email disguised as newsletter, and send them to any mailbox
+# without explict consent/subscription/confirmation.
+#
+# Their short URL service is also abused by phishers to hide the real destination
+# of the link, and they have no plan to fix it.
+#
+# They refuse to fix their platform abuse problem. Blocking them does more good
+# than harm.
+#
+# See also:
+# https://www.reddit.com/r/Substack/comments/123upme/didnt_subscribe_but_getting_emails/
+# https://www.reddit.com/r/Substack/comments/1bwxekz/never_experienced_so_much_spam/
+# https://medium.com/pitfall/how-bad-is-subscribing-spam-on-substack-02f3d228be82
+# https://om.co/2023/05/14/substack-spam/
+# https://news.ycombinator.com/item?id=43199314
+#
+# See also:
+# https://github.com/SukkaW/Surge/pull/98#pullrequestreview-4048399949
+.substack.com
+
 # --- AD Block ---
 
 # >> General AD