The Super User question "Playing mp3 in quodlibet displays “GStreamer output pipeline could not be initialized” error" is indexed under two URLs in Google:
https://superuser.com/questions/651591/playing-mp3-in-quodlibet-displays-gstreamer-output-pipeline-could-not-be-initia
https://superuser.com/questions/651591/playing-mp3-in-quodlibet-displays-gstreamer-output-pipeline-could-not-be-initia/652058
The first one is the canonical one; the corresponding rel
-canonical
is included in both pages:
<link rel="canonical" href="https://superuser.com/questions/651591/playing-mp3-in-quodlibet-displays-gstreamer-output-pipeline-could-not-be-initia" />
Google also indexed https://superuser.com/a/652058
, which redirects to the answer:
https://superuser.com/questions/651591/playing-mp3-in-quodlibet-displays-gstreamer-output-pipeline-could-not-be-initia/652058#652058
Now, the second URL from above is the same as this one minus the fragment #652058
.
So Google seems to strip the fragment, which results in exactly the same page under another URL (= containing the answer ID /652058
as suffix), and indexes it, too -- despite rel
-canonical
and duplicate content.
Shouldn’t Google recognize this and only index the canonical variant?
What is going on here?
EDIT: Google even displays a slightly different title for the same page (screenshot of result #1 and #2 for the query "Super User QuodLibet"):