How to handle when two answers are more or less the same?

Question

Sometimes questions will get two answers that are more or less the same solution to the problem posed, but perhaps worded differently or with equivalent, but superficially different, calculations.

I think that these cases are problematic because they:

1. Add noise to the question and to the site.
2. Potentially confuses the asker. I.e. the asker may wonder "what's the difference between these two answers"? The inevitable answer is "nothing. Both users just really wanted the points."

So how do we handle situations like this? Downvoting comes to mind, but it doesn't seem appropriate to downvote if the answer is indeed correct (and this could potentially lead to even more confusion for the asker). Should it be flagged? Should we leave a comment indicating that the second answer is the same as the first? Or is it best to just do nothing entirely, and refrain from upvoting and downvoting entirely?

Just wondering if there's a generally agreed upon practice for handling this situation.

Answer 1

Thanks for bringing this up. I think that the course of action is entirely situational. For example, there may be a complicated solution that took hard work to derive and write up, but it so happened that two people had the exact same idea and wrote essentially the same thing within a couple of minutes of each other. (This is not hypothetical - it happened here.) In this case, we elected to keep the solutions up with the understanding that one solution was posted first and the other was more or less equivalent.

In general, though, there are egregious "me too" solutions for any number of reasons. (Here's one source.) In these cases, the authors should be encouraged in the comments to either explain what value they are adding, or delete. In this case, I agree that downvoting is not the correct remedy unless there is something really wrong, but we can make it clear in the comments (and anyone who bothers to check the history will see for themselves anyway) that this is a "me too" solution that is best ignored.

Answer 2

it doesn't seem appropriate to downvote if the answer is indeed correct (and this could potentially lead to even more confusion for the asker).

I generally agree. I can imagine that in the more egregious cases, when a redundant answer is posted well after other, superior answers, a downvote may be warranted. But a comment is probably better.

Should it be flagged?

Definitely not. There is no basis for a flag.

Should we leave a comment indicating that the second answer is the same as the first?

This is a very reasonable thing to do, both for the benefit of the answerer (if they missed the earlier answer) and for other readers.

Or is it best to just do nothing entirely, and refrain from upvoting and downvoting entirely?

Also a reasonable thing to do, especially when neither the question nor its answers are of any lasting value.

Answer 3

I think that askers should not be underestimated. In general they are perfectly capable to understand that two identical answers are identical.

In my opinion, the best policy is to upvote the answer which appeared first (between two or more identical ones). Sometimes, however, this can be a delicate issue. Some people (it happened to me more than once) post something like "Hint: $a^2-b^2=(a-b)(a+b)$" in the first minute to be there first and subsequently edit the answer to write full solution.

Or it can also happen that one of the answers initially contains errors which are corrected afterwards. That can also be used to select one of the identical answers - though of course a theorem should not be named after the person who has corrected the last misprint in its proof.