Should we delete very late duplicate answers?

Question

Yup. Duplicate answers. We have seen some of them in last few days. Like this, this, this, this and possibly many more which I didn't mention. They aren't exact duplicates but they still have the same main answer.

Every duplicate answer is not bad. Some of them might contain some extra information which might not be in the original answer. Instead of posting another answer I would prefer to just comment on the original answer to add that extra information but I guess those kinds of duplicates are still okay. But the other kind of duplicates which have which have poor quality or contain no extra information. What should we do about them? Should we flag them? If yes, what reason should we choose (spam?, not an answer?, low quality?)? If no, should we let them stay there and just start downvoting until (if) the answerer deletes them? What is the solution?

EDIT: I am addressing only those duplicate answers which are posted after hours or days and not those which are posted in the difference of some few minutes.

Answer 1

Most such answers are by newcomers.
Silent downvoting is a great way to make them feel unwanted.

So I would suggest a polite comment and perhaps deletion after a few days.

Answer 2

I believe that in most cases we should comment and down-vote rather than simply delete.

The presence of a publicly visible answer with many down-votes and comments about it's redundancy seems a better discouragement then a deleted answer.

Notes:

If the duplicate answer came within about a minute of the one it duplicates (two different users solved the puzzle at effectively the same time) we should probably up-vote both and not make such a comment. (This is slightly flawed due to the fact that we can edit our posts after first creating them, but a repeated abuse of this feature should be noticed by regulars, and we can cross that bridge if we come to it).

If a duplicate answer adds more reasoning, is easier to understand, or adds value in some other way it should be left for community voting to decide.

If any answer has no reasoning, like the fourth example you provided, then we should comment, wait (an hour?) and then, if nothing has happened, down-vote it and vote to delete.