A talkNsText property would nicely complement the already existing subjectNsText property.
See: https://www.mediawiki.org/wiki/Extension:Scribunto/Lua_reference_manual#Title_objects
If there is no associated talk namespace, just gives nil (as the talkPageTitle property, and the talk property of the namespace data, do).
Use case: in a module I currently have to do:
local namespace = mw.site.namespaces[page.namespace] if namespace.talk then namespace = namespace.talk end local prefixedBase = namespace.name .. ':' .. base
With this property, I could do:
local prefixedBase = (page.talkNsText or page.nsText) .. ':' .. base