Wikipedia:Provide diffs

When making claims about the conduct of other editors, make sure to provide diffs as evidence.

Accusing editors of poor conduct

 * Any accusations raised against editors should be supported by diffs. The diffs should preferably be taken from the accused editor's own contributions, as opposed to diffs detailing the opinions of others. While an editor's block log may at times be informative, it can also prove misleading. By focusing on the editor's actual contributions, as opposed to the opinions others have formed about them, one is better able to ascertain if any wrongdoing has occurred.
 * The amount of evidence you need to provide depends on the scale of your accusation. If you accuse an editor of a one-time offense, one diff might be enough. However, if you are making accusation about the long term behaviour of an editor, you should be able to provide quite a few diffs to prove this. The provided diffs should be taken from over a lengthy timescale, and not just from one event or occurrence.
 * If you make an accusation and are proven wrong, redact your accusation and maybe, if you feel like it, consider issuing an apology.
 * When blocking, administrators should note the diffs that prompted their decision to block. While there are a few exceptions, it should normally not be a problem to add the diffs, even if blocking policy does not require you to do this specifically.