What is the appropriate course of action for a duplicate answer, especially one made several years after the fact?

Question

I have run into one or two "duplicate answers". They are technically correct, but they do not add anything new to the current answer. Furthermore, the current answer is often accepted, and several years old.

The one consensus I run into, on the Stack Exchange, is that such answers are demeritting to the purpose of Stack Exchange. We already have the information, but they add a general lack of quality, as well as failing to add additional information. In effect, they are just noise. However, the manner at which they should be dealt with often differs between down voting and flagging.

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To give one particular example, we have "How would I find the SDK folder for Android Studio so I can build my Unity project?".

The accepted answer was posted in February of 2015, and reads as follows:

"the sdk may be hidden in the AppDatafolder (the folder itself was hidden).

If you want to look for AppData, but can't find it, open explorer and type %appdata%, press enter. It will show the hidden files. Path will look like this; C:\Users\Your.name\AppData\Local\Android\sdk1 Now that you have found the sdk, go back in to unity and click EDIT / Preferences / External Tools. You will see a field for Android SDK location - enter the path in that field."

Recently, we have had an additional answer posted, which reads as follows:

"Go C:/user/username/appdata/local/sdk but some time it may be hiden if this floder hiden studio give error message like SDK tool directry missing"

Formatting aside, I can not see any value in the second answer. We already gain this information from the first answer.

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What should we do, in these situations? I find that on various exchange sites, the appropriate response can differ, but often boils down to two or three solutions:

• Simply downvote and comment, assuming that the answer will be deleted through the low-quality queue
• Flag for moderator attention, sighting "not a real answer", and assume the investigating moderator will realise the duplicate
• Flag for moderator attention, specifically commenting to say that this answer is a duplicate of the original answer.

Answer 1

I usually downvote the answer and leave a comment. If there is already a comment regarding the issue, I downvote the answer and upvote the comment.

I do this because the downvote button text says:

This answer is not useful.

which is the truth, as there is already one covering the issue at hand; it's not useful to have a second one.

I do this also because I believe that having more than one user acting upon the post will have a more impacting effect on the author than having a single one (a mod) delete the answer ("Boohoohoo, a mod on a power trip deleted my answer"), thus help us better show how the site works to the user.

It's not clear to me whether a user that has an answer deleted by a moderator or by the community is aware of it, but if not, that would be another argument to not have a mod simply delete the answer.

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The only 'downside' with downvoting the answer, as opposed to flagging for moderator attention, is that it's not free, it costs one rep. It's not an issue with users that have any significant amount of rep, but I would not be surprised that it discourages some users from using that downvote button.

This makes the process of eliminating low quality content slower than just flagging and having a mod delete the question. This could be a good thing (more people involved, community power, time for debate, you name it), or this could be a bad thing (bad content stays up for a longer period of time, the immediate feedback is the best to teach, but that's not what we get, etc.).