Is it appropriate to answer one's own question with code derived from another answer?

Question

I've come across this situation a few times, and I'm not sure what to make of it. A user will post a question, often there is a bug in his code that he cannot find. Someone, perhaps multiple people, post answers addressing the problem. Then, the user takes that information, fixes his code, and posts the revised now-working version as an answer. This often happens with newer users.

Here are recent (past 24 hours) examples:

Check of property type in Google App Engine model (see this answer)

How can I get Facebook Profile image from email? (see this answer)

jQuery UI Sortable and Cookie (see this answer)

Process.Start opens too many browsers in XNA game (see this answer)

When is this approach, using answer to fix and posting working code, appropriate? Always? Never? Only if ...? Should these answers be flagged for moderator attention? Should one leave a comment to the OP, and, if so, to what effect?

Answer 1

If the user gives credit to the sources, why not? At first I thought they might be gaming the system for points, but since that isn't what's happening, it should be OK.

Answer 2

It is actually a pretty common scenario that the answers help resolve the question but don't show the whole picture. So I actually consider it good if the OP posts the complete solution that resolved his problem again. Of course only as long as he credits sources for this solution.

Then there are answers like "The solution foo = bar worked for me! Thanks @AnonymousHelper!". Copying another answer doesn't make this a new answer, it should have been a comment - I flag things like this as "not an answer" then.

Answer 3

There's no issue if they're posting the code that actually works and it's significantly different from the code posted in the the other answers. Even better if they acknowledge the answer that pointed them in the right direction.

On a couple of the questions I've asked I've done just that and then accepted the original answer as it helped me the most. Without it I would have never got to the working code.

A comment might be appropriate (as Ben Lee suggests).

Answer 4

I think a comment to the OP is definitely appropriate. I like the wording used by someone who did just that (left the OP a comment) in your first linked example:

@BerserkerBernhard welcome to stack overflow! to help make the site better, here are some tips - if the answer helped you, you should upvote it. You should probably also mark it as accepted. – Peter Recore

Just a simple and polite "I know you're new here, so let me explain a bit how the system works".