Hope <source>, expand-templates and MediaWiki pages can auto convert(繁简转换).
I found, on Chinese Wikipedia and so on Chinese webs in MediaWiki, anything in <source> tag and so on (except <source inline>) seem not to be converted (see here). Maybe it should be controled by attributing to tags like source, nowiki and pre. What's more, MediaWiki (namespace) pages seem not either, except viewing the MediaWiki page. It make admins or bots creat subpages with converted content.
As for "此外，消息页面好像也不能繁简转换（除了查看相应的消息页面），而应该分别创建简体和繁体的子页面，这样很麻烦，除非用机器人。", @Nemo_bis this seems somewhat about translatewiki.net , and is it likely to support converter in all softwares that are localized on twn (even Blockly? Mantis? Mifos?)?
Thanks. <nowiki>s sometimes also need. About MediaWiki pages, I don't mean translate.net's translations. I mean user-custom, such as MediaWiki:Gadget-***, added sidebar and editnotices.