I propose that we change the installer to make Project:, rather than the wiki name, the default option for meta namespace Manual:$wgMetaNamespacename (i.e. namespace 4 https://www.mediawiki.org/wiki/Manual:Namespace#Built-in_namespaces). See bug 60168 https://bugzilla.wikimedia.org/show_bug.cgi?id=60168. Here is an image of what I have in mind that the installer should show: https://upload.wikimedia.org/wikipedia/mediawiki/b/b9/ProjectDefaultNamespac...
Rationales: 1) Standardizing the name makes life easier when people copy content from one wiki to another. E.g., if you import a template that links to Project:Policy rather than BarWiki:Policy, you don't need to edit the imported template, because it already links where it should.
2) Having the meta namespace name be the same as the wiki name causes collisions with interwiki prefixes when content is copied from one wiki to another. E.g., suppose FooWiki has an interwiki prefix linking to BarWiki (barwiki:) and then a user imports a template from BarWiki that links to BarWiki:Policy. That will now link interwiki to BarWiki's mainspace page "Policy" rather than to Project:Policy. It is not even possible to import BarWiki:Policy until the interwiki barwiki: prefix is first removed; the importer will say "Page 'BarWiki:Policy' is not imported because its name is reserved for external linking (interwiki)."
3) If you ever change the name of the wiki, you then have to change all the wikilinks to FooWiki: namespace; if it were Project:, they would stay the same. True, you can use namespace aliaseshttps://www.mediawiki.org/wiki/Manual:$wgNamespaceAliases, but that could defeat part of the point of rebranding, which is to deprecate use of the old wiki name.
4) We don't have any other namespace names (User, Template, etc.) that are, by default, different from one wiki to the next; what is the logic for making an exception for the meta namespace?