On https://www.mediawiki.org/wiki/Extension:WikiEditor the text "The button for adding user signatures (four tildes) is available on talk pages and in namespaces specified in $wgExtraSignatureNamespaces." appears to be wrong.
@Wikinaut: Ah, thanks. Please don't expect original authors of some code to plan to work on every single issue that might happen around that code base nowadays. Also see https://www.mediawiki.org/wiki/How_to_report_a_bug - thanks! :)
WikiEditor doesn't use $wgExtraSignatureNamespaces directly, but it calls mw.Title.wantSignaturesNamespace() to decide whether to display the button, and that uses $wgExtraSignatureNamespaces.
As far as I can see, the feature works correctly.
I had to deactivate the delete command in order to get that mechanism working for NS_MAIN - which I added in LocalSettings.php. I will try that again and report here whether it worked or not in the second trial.
It's not correctly working:
We have in LocalSettings:
define( "NS_PROJECTS", 500 );
define( "NS_PROJECTS_TALK", 501 );
define( "NS_SESSION", 502 );
define( "NS_SESSION_TALK", 503 );
define( "NS_ASSEMBLY", 504 );
define( "NS_ASSEMBLY_TALK", 505 );
$wgExtraSignatureNamespaces = [ NS_MAIN, NS_HELP, NS_STATIC, NS_PROJECTS, NS_SESSION, NS_ASSEMBLY ];
The additional Namesspaces NS_HELP, NS_STATIC, NS_PROJECTS, NS_SESSION, NS_ASSEMBLY are ignored.
@Wikinaut Glad you got it working. However, I must note that array( … ) and [ … ] are exactly the same. If changing one to the other fixed your problem, then I would guess that your configuration was correct from the start, but the script was cached in your browser and that's why you didn't see the effect immediately.