Voting to close something as a duplicate already does leave an automatic comment, attributed to you, saying:
Possible duplicate of [link to dupe target].
The only difference is that, under the current system, such comments are auto-deleted when the question is actually closed. If you're a gold tag badge holder, that means right away. For example:
If this information about the new system is correct, then the change will be essentially that the "possible duplicate" comment stays even after the question is closed. (OK, the automatic text is different, but you can still edit your own comment within the usual 5-minute window.)
To me, this isn't necessarily a bad thing. It makes sense to inform askers that their question may have been asked previously - both before and after their question is actually closed! In fact, if anything the comment is going to be more useful after the question is closed. Before closure, the question may not actually be a duplicate, and it's still able to attract answers. After closure, no more answers can come in, and it's really helpful to give the OP a notification so that they can either (a) see their answer on the dupe target or (b) clarify that their question isn't a dupe.
The only thing I'd really want to change is the wording. "Does this answer your question?" sounds a bit too ... uncertain, especially for someone who's wielding a hammer to close the question unilaterally. Maybe "This question has already been asked at ..."