Signing your posts on talk pages is required, and facilitates discussion by helping identify the author of a particular comment. Other users can then navigate to a talk page and address their comments to the specific, relevant user(s). Discussion is an important part of collaborative editing, because it helps all users to understand the progress and evolution of a work.
To sign and date a post, type four tilde characters (~~~~) or click the signature button in your edit toolbar at the end of your post. When the page is saved, these characters will be replaced with your username (with a link to your user page), a link to your user talk page, and a time stamp, like this:
Wikimedia Commons allows users to customize their signatures in their preferences, but a few rules exist to avoid disruption. The signature must unambiguously identify the author of a comment and must link to the user page, the user talk page or the user's contributions. The customized signature should be designed in a way that does not impair the readability of the page. If nicknames are used, make sure they can be attributed to a specific user. Forging signatures or deliberately concealing one's own identity will not be accepted.
- Signature templates are vandalism targets, and will be forever, even if the user leaves the project.
- Certain automated scripts (bots) are used to automatically archive particularly active talk pages. These bots read the source of the talk page, but don't transclude templates, and so don't recognize the template as a signature.
- Signature templates are a small but unnecessary drain on the servers. Transcluded signatures require extra processing—whenever you change your signature source, all talk pages you have posted on must be re-cached.
- Substitution of templates in signatures is discouraged, as any such template will be redundant to using the same content as a raw signature.
Simple text signatures, which are stored along with the page content and use no more resources than the comments themselves, avoid these problems.
- they are an unnecessary drain on server resources, and could cause server slowdown
- a new image can be uploaded in place of the one you chose, making your signature a target for possible vandalism and Denial-of-service attacks
- they make pages more difficult to read and scan
- they make it more difficult to copy text from a page
- they are potentially distracting from the actual message
- images do not scale with the text, making lines with images higher than those without
- they clutter up the "file links" list on the image page every time you sign on a different talk page
- images in signatures give undue prominence to a given user's contribution
One possible alternative is to use Unicode characters instead.
It is recommended that active Commons users with usernames that do not use the Latin alphabet (for example, Arabic, Chinese, or Hebrew usernames) add a Latin transliteration, translation, or nickname to their signatures (via Preferences → section “Signature” → options Signature: and Treat signature as wikitext (without an automatic link to your user page)). This makes it easier for users not familiar with those scripts to recognise and interact with such users. Similarly, users with Latin alphabet usernames who regularly interact with users of another script (such as Japanese), are encouraged to add a version of their username in that script.
In signatures of users with usernames in Arabic, Hebrew or other right-to-left scripts, the presence of text in both directionalities causes problems in some browsers. An example of such a signature is
which for some may display like "1 ,0:00 (talk) مثال January 2014 (UTC)" (see Bi-directional text: Unicode support).
This can be resolved by adding a left-to-right mark or LRM (‎) after the link to the user's page:
[[User:مثال|مثال]]‎ ([[User talk:مثال|<span class="signature-talk">talk</span>]]) 0:00, 1 January 2014 (UTC)
- → مثال (talk) 0:00, 1 January 2014 (UTC)
In the "Signature" section of your preferences, you can change your signature to include a left-right mark. If your comment itself is in a right-to-left script, it may be necessary to precede your signature with another LRM (otherwise part of the signature will be displayed before the comment).