Justify the rules for duplicate

docs/DeveloperGuide.md

@@ -392,7 +392,8 @@ Priorities: High (must have) - `* * *`, Medium (nice to have) - `* *`, Low (unli
 
       Use case ends.
 
-**Use case: UC04 - Add tags to a contact**
+**Use case: UC04 - Add tags to a contact**  
+
 **Precondition**: Contact to add tags to already exists
 
 **MSS**
@@ -418,7 +419,8 @@ Priorities: High (must have) - `* * *`, Medium (nice to have) - `* *`, Low (unli
 
       Use case ends.
 
-**Use cases: UC05 - Delete a tag from a contact**
+**Use cases: UC05 - Delete a tag from a contact**  
+
 **Precondition**: Contact to delete a tag from already exists
 
 **MSS**
@@ -508,7 +510,9 @@ before the command was executed.
 * **Field**: An attribute possessed by a contact, namely Phone number, Tags, Name and Email.
 * **Prefix**: An identifier used in commands to indicate which field is referred to. For the 4 fields Phone, Name, Tags and Email,
     the *prefixes* would be `p/`, `t/`, `n/` and `e/` respectively.
-* **Duplicate Contact**: A contact that has the same Phone, Email or Name as another contact.
+* **Duplicate Contact**: A contact is considered a duplicate if it shares the same phone number, email, or name with another contact. 
+    Phone numbers and emails are unique identifiers, so allowing duplicates could cause confusion, such as accidentally contacting the wrong person. 
+    Unique names also help maintain organization, with small variations (e.g., capitalization or adding a number) used to distinguish individuals with the same name.
 * **Tag List**: The scrollable list in the GUI displaying all unique tags and their colour-coded categories.
 * **Person List**: The scrollable list of contacts in the GUI displaying all contacts and the respective values for their fields.
 * **Commands affected by `undo` and `redo`**: These refer to all commands that affect the *state* of the Tag List and Contact List

docs/UserGuide.md

@@ -77,6 +77,7 @@ any traditional point-and-click management app.
 
 **Notes about duplicate contacts:**<br>
 * A contact is considered a duplicate of another if it has the same Name, Phone or Email as the other contact.
+* 
 
 --------------------------------------------------------------------------------------------------------------------
 
@@ -123,6 +124,9 @@ Format: `add n/NAME p/PHONE_NUMBER e/EMAIL [t/TAG]…​`
 
 * The phone number must follow the Singaporean convention: have 8 digits, start with 6, 8, or 9, and consist only of numbers.
 * Duplicate contacts cannot be added to the list.
+* Names are case-sensitive. For example, “Alice” and “alice” are considered distinct names.
+* Names should only contain alphanumeric characters and spaces, and it should not be blank.
+* In cases where two people share the same name, differentiate them by appending a number or changing the capitalization (e.g., “Mary” and “Mary 2”).
 
 Examples:
 * `add n/John Doe p/98765432 e/[email protected]`