diff --git a/index.rst b/index.rst
index 4d3649b..03d8c22 100644
--- a/index.rst
+++ b/index.rst
@@ -51,9 +51,9 @@ Terminology
 
 In EditorConfig:
 
-- "EditorConfig files" (usually named ``.editorconfig``) include section(s)
-  storing key-value pairs.  EditorConfig files must conform to
-  this specification.
+- "EditorConfig files" (named ``.editorconfig`` in lowercase) include
+  section(s) storing key-value pairs. EditorConfig files must conform to this
+  specification.
 - "Cores" parse files conforming to this specification, and provide
   key-value pairs to plugins.
 - "Plugins" receive key-value pairs from cores and update an editor's
@@ -185,7 +185,7 @@ If the glob contains a path separator (a ``/`` not inside square brackets), then
 to the directory level of the particular `.editorconfig` file itself.
 Otherwise the pattern may also match at any level below the `.editorconfig`
 level. For example, ``*.c`` matches any file that ends with ``.c`` in the
-directory of ``.editorconfig`` or any other directory below one that stores this ``.editorconfig``. 
+directory of ``.editorconfig`` or any other directory below one that stores this ``.editorconfig``.
 However, the glob ``subdir/*.c`` only matches files that end
 with ``.c`` in the ``subdir`` directory in the directory of ``.editorconfig``.
 
@@ -202,11 +202,11 @@ File Processing
 
 When a filename is given to EditorConfig a search is performed in the
 directory of the given file and all parent directories for an EditorConfig
-file (named ".editorconfig" by default). Non-existing directories are treated
-as if they exist and are empty. All found EditorConfig files are
-searched for sections with section names matching the given filename. The
-search shall stop if an EditorConfig file is found with the ``root``
-key set to ``true`` in the preamble or when reaching the root
+file. An EditorConfig file is named ".editorconfig", all lowercased.
+Non-existing directories are treated as if they exist and are empty. All found
+EditorConfig files are searched for sections with section names matching the
+given filename. The search shall stop if an EditorConfig file is found with
+the ``root`` key set to ``true`` in the preamble or when reaching the root
 filesystem directory.
 
 Files are read top to bottom and the most recent rules found take
@@ -214,6 +214,23 @@ precedence. If multiple EditorConfig files have matching sections, the rules
 from the closer EditorConfig file are read last, so pairs in closer
 files take precedence.
 
+Capitalization of the File Name
+-------------------------------
+
+As noted above, the ``.editorconfig`` filename should be lowercased. On some
+platforms, opening a file with a different capitalization results in opening
+the same file with lowercased file names. On such a platform, in addition to
+the all lowercased ``.editorconfig`` file name, a Core may choose to also
+accept files with a different capitalization as if it were all lowercased.
+
+*(informative)* Such platform is common with a case-insensitive filesystem.
+For example, a file named ``.editorConfig`` exists in the filesystem, but
+opening a file named ``.editorconfig`` via a file-opening API still opens the
+differently capitalized ``.editorConfig`` file. The behavior of the Core as
+described in the previous paragraph is to prevent the need of the additional
+operation of specifically retrieving the filename, which can be relatively
+expensive in the context of EditorConfig.
+
 .. _supported-pairs:
 
 Supported Pairs