I had always seen questions that are closed as duplicates with the following message at the top of the post:
This question already has an answer here:
[link to existing question] X answers
Here is a sample screenshot of a recently closed question:
Today I noticed that some duplicate questions have a different message:
[link to existing question]
Here is a sample screenshot of such a question:
It seems odd that different questions should have different duplicate messages. The first message is more direct; it tells you that the question already has an answer, and it tells you how many answers there are. The second message is possibly more accurate, as it is possible for a question to be closed as duplicate even if it does not have an answer elsewhere. Additionally, the wording "possible duplicate" seems more in line with the reality that questions can be reopened at any time. But regardless of which message is better, it should surely be standardized across all questions.
More importantly, the second message suffers from a serious flaw. It is apparently not an external note pinned to the question, but merely added into the text of the post:
As such, anyone with edit privileges can simply remove it, with the result that there is no longer a duplicate message displayed:
This seems to be a problem.
Additionally, when it comes to the question containing the first message, I have the ability (due to a gold tag badge) to edit the duplicate list:
But when it comes to the question with the second message, that option no longer exists (even though it's the same tag where I have the badge):
Given that this is the first time I've seen this, I'm not sure if it's always been this way or if something recently happened to change something. I will note that all the questions that I've seen the second version of the message on are old questions. Either way, this seems like something that should be fixed.