Categories are very important for Wiktionary. We use them to group words by language, part of speech, register, topics, rhymes and many other groupings, as well as for maintenance purposes.
However, the category listings are very bare-bones. In particular, in language-specific categories, we would like the entries to be formatted correctly according to our rules for that language.
For instance, when you visit a category of Greek words (such as - an example at English Wiktionary - wikt:Category:Greek nouns), the user should see Latin-script transliterations next to the Greek script, just as they do anywhere a Greek word is mentioned in an entry, thanks to our use of templates. We already have Lua modules to do this work within the entries themselves - we just need a way to allow these modules to be run against the page list on a category page.
Proposed solution: Develop some kind of magic word that is placed in the category wikitext. This magic word tells MediaWiki that, every time a user views the category, each page title to be displayed should be passed into a Lua module, which then transforms the title for display.