The message visualeditor-descriptionpagelink is a link to a local wiki page about Visual Editor. Its current English value is "Project:VisualEditor", and the documentation says "Do not translate "Project"; it is automatically converted to the wiki's project namespace."
Since it's not supposed to be translated anyway, instead of saying this to translators, the "Project" part should just be removed from the message and inserted automatically in software.
That would prevent local communities from changing this to a page in a different namespace, e.g. "Help". Especially, in de.wikipedia, this indeed is the case: https://de.wikipedia.org/wiki/MediaWiki:Visualeditor-descriptionpagelink
This is not a blocker, and if a particular wiki really wants to have it in a different namespace, it can be resolved using a redirect.
This is one of the most used messages, so it is one of the first messages that are translated to every language. They should be easier to translate, not harder. Having to write an unnecessary word makes things unnecessarily harder, even if it's "just" copying. New translators often make mistakes in such messages, and instead of teaching them, the messages should just be simpler.
I'm not convinced we should change it… Maybe it would be easier for translators, but it would be harder for communities wishing to customize the link, as @Schnark points out. (Although we could probably do something to make it default to the 'Project:' namespace if none is specified, like the template syntax {{Foo}} defaulting to Template:Foo; but then it would not be obvious that it works this way.)
If we wanted to change it, then most of all we should make all similar messages consistent, and currently all similar messages also include the namespace. This message in VisualEditor was made to be consistent with them. Examples from MediaWiki core are aboutpage, currentevents-url, disclaimerpage, policy-url, portal-url, privacypage, as well as copyrightpage, grouppage-user, grouppage-autoconfirmed, grouppage-bot, grouppage-sysop, grouppage-interface-admin, grouppage-bureaucrat, grouppage-suppress (which use {{ns:project}}: instead of just Project:, but it amounts to the same thing).