MAINT: extend comment

Author: dnicolodi

tests/test_tags.py

@@ -29,13 +29,22 @@
 
 
 def get_abi3_suffix():
-    # EXTENSION_SUFFIXES are ordered in preference order, and more specific ABI is preferred.
-    # On free-threaded 3.15+, this will match ".abi3t" as the only supported stable ABI.
-    # On GIL-enabled 3.15+, it will match plain ".abi3" first, since that ABI is more specific.
+    """Get the filename suffix identifying stable ABI extension modules."""
+
+    # EXTENSION_SUFFIXES is ordered from the more to the less specific ABI.
+    # On Python 3.15 or later, this resolves to ``.abi3t-${arch}`` for
+    # free-threaded builds and to ``.abi3-${arch}`` on regular builds.
+    #
+    # Older Python versions do not support a stable ABI for free-threaded
+    # builds, and do not support a platform-specific filename suffix, and
+    # this resolves to simply ``.abi3``.
+    #
+    # On Windows, Python does not use a dedicated filename suffix for stable
+    # ABI extension modules, and this resolves to ``.pyd``.
     for suffix in importlib.machinery.EXTENSION_SUFFIXES:
-        if '.abi3' in suffix:  # Unix
+        if suffix.startswith('.abi3'):
             return suffix
-        elif suffix == '.pyd':  # Windows
+        if suffix == '.pyd':
             return suffix