Added user story 3

active/39-chat-moderation/user-stories/us-1-blocking-a-user.md

@@ -13,6 +13,7 @@ Any reason *User A* doesn't want to see posts of *User B* anymore.
 
 - *User A*
 - *User B*
+- *User C*
 
 ## Pre-Condition
 

active/39-chat-moderation/user-stories/us-3-filter-unwanted-content.md

@@ -0,0 +1,43 @@
+# User Story 3: Filter unwanted Content
+
+## Description
+
+*User A* does not want to view any messages that contain the phrase x. *User A*
+updates their moderation rules to ignore any messages that contain the phrase x.
+Messages that contain the phrase x no longer appear in any chat feeds of *User A*.
+
+## Trigger
+
+Feeds of *User A* contain a phrase the user doesn't want to see.
+
+## Actors
+
+- *User A*
+- *User B*
+
+## Pre-Condition
+
+*User A* discovers phrases she dislikes and decides to ignore these messages.
+
+## Post-Condition
+
+After adding a phrase to ignore no more messages containing this phrase are
+in the feed of *User A*.
+
+## Flow
+
+- *User A* discovers unwanted phrase.
+- *User A* decides to filter this phrase out.
+- *User A* opens a (global|chat room) menu and selects the menu point
+  for filtering.
+- *User A* adds a phrase to filter.
+
+## Remarks
+
+- Question: Does a phrase ban of a user effects only one chat room or all
+  chats of *User A*?
+- Question: Does the *User A* get a kind of notification of an unwanted phrase
+  by *User B*, e.g. to allow her to react on it?
+- Question: Which options for filters? Exact match, full words, wildcards,
+  regular expressions?
+- Todo: Add user stories for the changing and the removal of filter phrases.