Moderator Deletion of Equivalent Answers?

Question

Two days ago, Mark Byers and I gave essentially equivalent answers to Replacing particular elements in a list.

Today, a moderator deleted Mark's answer.

Now, if there was something technical wrong with it or met both of the following criteria I probably wouldn't say anything:

1. It was posted after mine
2. It was unambiguously included in mine from the time both were posted.

However, it was a perfectly accurate answer and it doesn't meet the 2nd criteria. The answering went like this:

1. I posted my answer. It was incorrect.
2. I immediately noticed and fixed my answer.
3. While I was editing Mark posted his answer (six seconds after mine).
4. Mark commented on mine that it was incorrect.
5. I responded that I'd already fixed it.
6. We both deleted our comments.

Because his was correct first, his was originally (and correctly) upvoted over mine. Over time, my answer slowly caught up (it contained slightly more info).

Shog9's answer to What's the appropriate etiquette when two people correctly answer a question at the same time? suggests that there isn't any sort of rule about this -- it should have been at my and Mark's discretion whether or not do delete our answers.

Was the deletion the result of a flag? Was it deleted because it had become "noise" because my answer was (slightly) more complete?

I think in this case he deserved some upvotes because his was the first correct answer, and that his answer should be undeleted.

Answer 1

Over time, my answer slowly caught up (it contained slightly more info).

This is by-design! Ideally, Mark would have responded the way you did (and the he did post-deletion): by adding additional information or clarity to the answer. Can't fault an answer for being a duplicate if it isn't!

To answer your other question: yes, the deletion was done in response to a flag. Truly identical answers are noise - imagine someone else added a better answer later on - it would be ordered below the two duplicates initially.

That said, it isn't normal for moderators to delete duplicate answers unless there is a serious glut of answers - two short ones doesn't really present a problem for future readers. I might down-vote one of them though. However, I've a hard time faulting the moderator here - the answers were extremely short, largely identical, and yours had slightly more auxiliary information.

See also: How aggressively should we maintain and improve very popular questions?

Answer 2

Posts that are entirely redundant are noise, and should be removed. However, if someone makes a useful post, they shouldn't lose the points just because a better answer comes along and makes them redundant.

There've been a few times times where I've seen a question where several answers had become redundant, but was hesitant to flag them because it would be unfair. I'm not sure about the details, but some sort of Delete/Hide as Reundant option might be appropriate for cases like this. Perhaps it could be made available to users with a high enough score in the question's tags.