Hi @Oeyvindg, thanks for taking the time to report this! Please always include MediaWiki and Page Forms version information - thanks!

Thank you @Aklapper, added to description.

@Oeyvindg - yes, that behavior is on purpose. The idea is that this gives the form/template designer more flexibility - because then they can have the template add the namespace prefix to the value (or values, using #arraymap), or not. An obvious example is if the field holds a file name. The template could then display that value as:

[[File:{{{TheFile|}}}|{{{TheFile|}}}]]

Is the differing behavior then on purpose in regards to the other autocompletes, like category and (SMW) property (I Did not check the behaviour here)? I.E if you are autocompleting on a category, you most likely want the namespace prepended, but if you autocomplete on namespace, there are other use cases?

I see I'm mostly thinking of how things work from my semantic/RDF centric data view.

Yes, it's different on purpose. With anything other than "values from namespace", the values returned can be in different namespaces - so the page names have to contain the namespace. It's a little confusing, but I think this is the best solution.