I tried to use {{DISPLAYTITLE: ... }} for a test of its behaviour,
i.e. without wanting to safe a page, in the English Wikipedia.
Inserting {{DISPLAYTITLE: ... }} in an arbitrary page and
inspecting it's preview did not achieve anything.
Assuming that, DISPLAYTITLE might only be working when an
existig page is rendered, I inserted it in the page Wikipedia:Sandbox
but found, it influences neither the preview not the saved version
of the page.
I suggest that, also page preview should honor {{DISPLAYTITLE: ... }}
Version: 1.16.x
Severity: normal