Add note re: side effects to "Delete post" procedure in "Moderator instructions"

Author: per1234

content/categories/staff/moderation/_topics/moderator-instructions/1.md

@@ -680,6 +680,13 @@ Closing a topic will prevent any further replies by non-staff users.
 
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+⚠ If you delete the first post in the topic, the entire topic will be deleted. In the case where there is valuable information in replies on the topic, consider alternative approaches that will not result in the loss of those valuable contributions:
+
+- Instead of deleting the post, [edit out the unacceptable content](#edit-post).
+- [Split the valuable replies out to a separate topic](#split-topic) prior to deleting the problematic topic.
+
+---
+
 1. Follow the ["**Flag post**" instructions](#flag-post), deleting the post through the resolution of the flag.
 
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