Add info about calling remove() on nodes that have no parent node (#40274)

Add info about calling remove() on nodes that have no parent node

Author: lionel-rowe

files/en-us/web/api/characterdata/remove/index.md

@@ -8,7 +8,8 @@ browser-compat: api.CharacterData.remove
 
 {{APIRef("DOM")}}
 
-The **`remove()`** method of the {{domxref("CharacterData")}} removes the text contained in the node.
+The **`remove()`** method of the {{domxref("CharacterData")}} removes it from its parent node.
+If it has no parent node, calling `remove()` does nothing.
 
 ## Syntax
 

files/en-us/web/api/documenttype/remove/index.md

@@ -9,6 +9,7 @@ browser-compat: api.DocumentType.remove
 {{APIRef("DOM")}}
 
 The **`DocumentType.remove()`** method removes a document's `doctype`.
+If it is already detached from the document, calling `remove()` does nothing.
 
 ## Syntax
 

files/en-us/web/api/element/remove/index.md

@@ -8,7 +8,8 @@ browser-compat: api.Element.remove
 
 {{APIRef("DOM")}}
 
-The **`Element.remove()`** method removes the element from the DOM.
+The **`Element.remove()`** method removes the element from its parent node.
+If it has no parent node, calling `remove()` does nothing.
 
 ## Syntax