Short answer here is that we're aiming to facilitate what we think is the core utility of these comments... We might be wrong about that utility, or wrong about whether our change helps more than it hinders - but determining that will take time and effort.
Yaakov has marked your request as "deferred" to indicate that, while we believe your concerns likely have merit, we can't address them right now; we'll revisit this in the future once we have a better idea of how best to do so. Please see Yaakov's answer for a final update.
The rest of the story
It's worth remembering when discussing these things that they are a combination of system behavior and social convention. Duplicates were originally implemented exactly like every other close reason - there was no special behavior, no extra support for recording or displaying links, etc. Most of the behavior we now have either started out as a practice among users, or was created to replace such a practice... In some cases, both. We didn't design this system so much as we paved the "desire paths".
When we're looking at something like this comment, born of the complex maelstrom described above, we gotta ask first: why would folks want a comment? What purpose does it serve in the context of interpersonal interaction? Why is that fence there?
Here's what I see:
For the asker, such a comment...
- ...provides an inbox notification, letting them know that there is potentially an answer to be had, or perhaps instead a misconception to clear up.
- ...provides an entrypoint into a conversation regarding the merits of the suggested duplicate (that is, it is possible to reply to a comment; it is not possible to reply to a vote).
For the voter, such a comment...
- ...implicitly encourages interaction and discussion over the merits of the proposed duplicate, setting the tone for such an interaction.
- ...ensures that they can be made aware of feedback regarding the proposed duplicate (from the asker or from others) (again, no one can @-notify a voter)
For other readers / voters, such a comment...
- ...lets them know that the question is possibly a duplicate, and provides them with details on the proposed original (3rd-party readers cannot see this information at all unless they have close privileges; even those with closing privileges can only see this information by opening and navigating through the close dialog). The system automatically upvotes the comment as more voters choose the same option, thus ensuring that it grows more visible as the question moves closer to being closed.
- ...provides fast access to what is at least a related question, even if the question is never closed.
- ...ensures that the system cross-links both questions in the sidebars of both posts (such links are not otherwise added to PostLinks unless/until the post is actually closed).
Now. Not all of these effects are equal in their utility, nor are all well-served by a comment. However, it is likely that they have some non-trivial importance, as other approaches were possible and were tried by some or many users in the time prior to the system supporting this one directly (editing body, editing title or tags, answering, etc). IOW: the organic solution may not be optimal, but it likely won out over alternatives due to various practical advantages such as those sketched out above. In order to replace it, we need not replicate its total functionality, but we must improve on its utility to such an extent that users do not just fall back on leaving such comments manually (at which point we would have no influence over their content or tone). And any change short of replacing it should strive to improve one or more of the known utilities without unduly hurting the rest.
Facilitating conversation without hiding information
At last that brings us to the change in wording. Going back to the charter for these changes, where Meg laid out three key priorities:
- Delivering improved, private feedback to post authors
- Not putting users who curate content on the spot
- Giving actionable, understandable information for the vast majority of public viewers
Now, this isn't private feedback; we're working on ideas there, but right now duplicates are public - unless the asker deletes their question, it sits there visible to the world. We don't have a facility for private (or even slightly out of the way) discussion, and even if we did have one putting such a comment there would hurt the utility for other readers and voters (see above) - as long as the question itself is publicly visible, any discussion surrounding it needs to be as well...
...But, perhaps we can do this while reducing friction between the folks identifying duplicates and the folks asking them. The hope is that this wording works toward that end...
...But does it?
Well, we ran an A/B test for about a month with this new wording. Folks from both groups were flagging or voting to close questions as duplicates, so I compared the frequency with which those comments resulted in replies, edits, and flags (on the auto-comment).
...there was effectively no difference. Replies hung around 19%, edits around 27%, flags around .2%.
IOW: we have no hard data suggesting that this is better or worse. All we have to go on is folks like you, and reports from folks asking questions. Those are both useful, but they take time to collect and interpret.
So... We'll keep watching this, and make adjustments as the long-term effects become more clear.