Notify of posts that the user already responded to

I've decided that this is a pointless behaviour - personally I'd much
rather want the guarantee that I'm going to be notified of a post.
Otherwise a vigilant user might fear that the notifications system
doesn't actually work.

There may well be users who depend on this behaviour and I'm sure
they'll pipe up.

If in the future I choose to reimplement this behaviour, I should run a
migration to remove posts that are no longer relevant because of it.

notifier/database/queries/get_posts_in_subscribed_threads.sql

@@ -31,11 +31,6 @@ FROM
     AND thread_sub.thread_id = thread.id
     AND thread_sub.post_id IS NULL
   )
-  LEFT JOIN
-  post AS user_response_child_post ON (
-    user_response_child_post.parent_post_id = post.id
-    AND user_response_child_post.user_id = %(user_id)s
-  )
 WHERE
   -- Remove deleted posts
   post.is_deleted = 0
@@ -59,9 +54,6 @@ WHERE
 
   -- Remove posts in threads unsubscribed from
   AND (thread_sub.sub <> -1 OR thread_sub.sub IS NULL)
-
-  -- Remove posts the user already responded to
-  AND user_response_child_post.id IS NULL
 ORDER BY
   wiki.id,
   category.id,

notifier/database/queries/get_replies_to_subscribed_posts.sql

@@ -33,11 +33,6 @@ FROM
     AND post_sub.thread_id = thread.id
     AND post_sub.post_id = parent_post.id
   )
-  LEFT JOIN
-  post AS user_response_child_post ON (
-    user_response_child_post.parent_post_id = post.id
-    AND user_response_child_post.user_id = %(user_id)s
-  )
 WHERE
   -- Remove deleted posts
   post.is_deleted = 0
@@ -60,10 +55,8 @@ WHERE
   )
 
   -- Remove replies to posts unsubscribed from
+  -- Sub table is added to this query via left join, so the null check matches when the user has no manual subscription to or from a post
   AND (post_sub.sub <> -1 OR post_sub.sub IS NULL)
-
-  -- Remove posts the user already responded to
-  AND user_response_child_post.id IS NULL
 ORDER BY
   wiki.id,
   category.id,