What is a good edit, which edits may be bad?

Question

Since it came up recently there appears to be some confusion as which edits are welcome and which edits should be rejected or rolled back.

We know, that whenever an edit improves a post it was a good edit but we may want to better define what we think such an improvement is.

Answer 1

Only for questions:

If a question has already been answered, and gets changed in a way which renders some answers false, the change shouldn't be made. Instead, if the question was unclear, the person who did a poor job asking it shall open a new question, keeping the already given but else useless answer intact.

I observed cases (not on GL) where correct answers where downvoted after the question was rephrased, getting a different meaning. This should be avoided if the uncorrected question is a legitimate, different one.

Answer 2

Any time you see a post that needs improvement and are inclined to suggest an edit, you are welcome to do so.¹

However, edits should not be an end in itself but should be a value-adding activity. The aim of edits is to increase the probability of enhancing the satisfaction of readers.

Edits are expected to be substantial and to leave the post better than you found it.¹

Thus, edits should be effective; the improvement should not be negligible.

If the edit makes no improvement whatsoever, it should be rejected.

This edit fails to make the post even a little bit easier to read, easier to find, more accurate or more accessible. Changes are either completely superfluous or actively harm readability.²

On German Language Stack Exchange, any correction of the German text is considered a relevant improvement and is therefore a justified edit. The term correction is generally defined as ‘action to eliminate a detected nonconformity’. Here, nonconformities may relate to orthography, grammar, punctuation, or typography.

Edits are not limited to corrections. Posts may be improved by additions or by changes of the wording. However, such improvements can affect the message and intentions of the post. In this respect, the requirements for editors are similar to those for translators: Editors should provide corrected or otherwise improved versions that accurately preserve the message and intentions of the original post. Faithful edits retain both the intention of the original author and the style and register of the language used.

Edits to questions should not affect the choice of the right answer. In particular, edits to questions should not invalidate any already given answer. (This also applies to the original author of the question. If necessary, a new question may be asked.) Edits to answers should not affect the conclusions from the answer.

If the edit deviates from the original intent of the post, the original author may want to consider rejecting the edit. Edits that clearly conflict with the author’s intent should be rejected.

This edit deviates from the original intent of the post. Even edits that must make drastic changes should strive to preserve the goals of the post’s owner.²

Nevertheless, mere corrections as defined above should not be rejected. (This also applies to the original author of the post.)

If you are not comfortable with the idea of your contributions being collaboratively edited by other trusted users, this may not be the site for you.¹

Answer 3

The following summarizes our view on good or bad edits as was seen from related meta posts (see below), comments, and chat discussions we had over time:

• it edits typing errors, corrects punctuation, adds formatting:
  This may look too minor at first sight but we are a language site. We should not tolerate minor mistakes but we should edit them, the quicker the better. Comments are o.k. but if on questions they may hang around too long. If an error was not corrected it may provoke answers leading away from the question, and the answers will need an edit too after such an error was edited. Adding formatting to a post is welcome of it led to a consistent site's appearance and improved legibility but we should not overdo this.
• it improves the overall grammar:
  That's what we expect of a good edit. If the grammar was not subject of a question, or if it was in an answer we should not hesitate and improve the post. Advanced speakers of German will be grateful to see that somebody cares, and beginners will learn a lot from this.
• it adds additional information from comments:
  We should highly encourage this, as an overlong comment thread is cumbersome to read, and valuable information may easily be overlooked. It is much better we had included this in a question or answer to then flag the comment as obsolete for clean-up. If the OP had no time to edit I see nothing wrong if we did that for them.
• it adds a missing link, a quote or other reference:
  This may be very valuable as it supports the content with an other resource. However we should take care that any such link is of value indeed. If it was overt spam it should be removed immediately, if it was any doubtful AskJaqueline.com site we may not want to support them with a link. If it was a link prone to be dead soon it may not help in the long run. Such links should not stay. Any verbatim quotes should state their source.
• it adds an additional point not made so far:
  Sometimes an otherwise good answer (rather than a question) is missing some details or aspects. Then we have the choice to write another answer (which then will likely be incomplete), comment on the post (which may be overlooked easily), or edit those points into the answer, just as we would do on a Community Wiki post. By editing we may turn a good answer into a great answer, which I believe we should encourage. Take the reputation point the original poster may get in addition as a reward for making this possible at all. At the end the resulting good content on our site is what counts. If these additions did not add any value they should be removed.
• it adds a whole paragraph of additional information:
  If this considerably improved the post it is welcome, but if there was only a minor benefit we may leave it to the OP and may better comment. In case absolutely no value was added we may safely roll back such an edit.
• it edits the post in a way that the original content was lost or conclusions were reverted:
  This is an edit we usually do not accept. However in rare cases we may have tried to salvage a poor question or answer which otherwise would have to be deleted. These cases should be an exception and may only be needed in case there is good content from answers. We should add a comment explaining the reason behind such an edit.

• it removes content:
  Valuable content should not be deleted. We keep an eye on those "destructive" edits to make sure this does not happen. Note that this is not meant for removing salutations, Glad-I-found-yous, and Thank-Yous. Removing these helps to keep posts clear and to the point. That is why editing such sections out is encouraged on all Stack Exchange sites. We should not be different.

• it adds plain wrong information:
  In these clear-cut cases an edit is not welcome and should be rolled back.

If we are unsure we should discuss matters in the German Language Chat.

Read also these related posts:

How to handle typos that are significant in respect to why the question came up?
Where do I find help on formatting my post?
Let us clean up comments
Spelling mistakes in questions
Some guy corrected 99 out of 100 errors in a post. Should I correct the remaining one and steal the credit to that guy?
How to avoid too many edits from different users?
Should we change """" to "„“" in German questions?
Editing orthographic errors
Is my edit appropriate?

On general SE Meta:

What are the guidelines for reviewing?