List of steps to reproduce:

• On Chinese Wikipedia, visit Special:無跨維基連結頁面 (zh-hant, defined here), "no such special page"; visit Special:无跨wiki链接页面 (zh-hans, defined here), redirected to Special:Withoutinterwiki normally.
• Edit sandbox with content {{顯示標題:test}} (zh-hant, defined here) and preview, it will be parsed as a template rather than a magic word; {{显示标题:test}} (zh-hans, defined here) works normally, page title is changed to "test".

As zh-hans and zh-hant coexist on zhwiki, aliases and magic words in both variants should work.

Chinese Wikipedia uses language code zh, but a lot of entries are missing (comparing with MessagesZh_hans.php) in MessagesZh.php, which will fallback to zh-hans, so many zh-hant aliases/magic words do not work. Those missing $specialPageAliases and $magicWords should be included in MessagesZh.php. Including zh-hant variants in MessagesZh_hans.php should also work but may be not appropriate as it is a fallback language.