The closest thing to documentation that I've been able to find, in English at least, is http://meta.wikimedia.org/wiki/Automatic_conversion_between_simplified_and_traditional_Chinese. It's not very useful for developers interested in learning how the system works, though. I suspect there may be more documentation in Chinese somewhere on zh.wikipedia, but if so, I don't know where and it wouldn't be of any use to me anyway since I can't read Chinese.

FYI:

• {{GROUPCONVERT:...}} was removed in r51405
• There is more information about the conversion system at
  • http://zh.wikipedia.org/wiki/Help:%E5%AD%97%E8%AF%8D%E8%BD%AC%E6%8D%A2%E8%AF%AD%E6%B3%95
  • http://zh.wikipedia.org/wiki/Help:%E4%B8%AD%E6%96%87%E7%BB%B4%E5%9F%BA%E7%99%BE%E7%A7%91%E7%9A%84%E7%B9%81%E7%AE%80%E3%80%81%E5%9C%B0%E5%8C%BA%E8%AF%8D%E5%A4%84%E7%90%86

(It is more or less readable using a translator)

Helder

I started a page at http://www.mediawiki.org/wiki/Writing_systems.

more documentation of the LanguageConverter and variants would be super helpful. :)

right now I need to look at the code, ask certain people or make a guess as to why things are done the way they are.

The entire w:zh:H:AC page is worth translating into an independent page for LanguageConverter. mw:Writing systems/Syntax should probably be moved to a page under the new LC page after its created. "User friendly" or "cheatsheet" info in w:zh:Help:手工字詞轉換 should be merged into the Syntax page. Some big good TODOs.

There's also https://www.mediawiki.org/wiki/Specs/HTML/1.5.0#Language_conversion_blocks now, although that's pretty technical.

Another thing which needs cleanup: https://www.wikidata.org/wiki/Talk:Q15630179 (how to describe those LC-related items on Wikidata ?)