Automatic conversion between simplified and traditional Chinese
meta.wikimedia.org
meta.wikimedia.org
Probably because > 90% of native Chinese speakers use the simplified script. Now, I don't know what Wikipedia statistics are -- maybe usage skews heavier in areas where traditional characters are used, so that would be a reason to not do so, or to ask first. But without that information, defaulting to the more-commonly used script seems like a reasonable measure.
For example, the page on Cryptography https://zh.wikipedia.org/wiki/%E5%AF%86%E7%A0%81%E5%AD%A6 contains both 密码学 and 密碼學, sometimes in adjacent sentences.
If you select the versions for Mainland China https://zh.wikipedia.org/zh-cn/%E5%AF%86%E7%A0%81%E5%AD%A6
or Taiwan https://zh.wikipedia.org/zh-tw/%E5%AF%86%E7%A0%81%E5%AD%A6
those get cleaned up to the appropriate shape.
Edit: not sure if it’s the correct parameter. But something like that exists for Wikipedia.
1. character to character conversion - originally based on tables from unicode
2. word/phrase type structure level matching - based on their own lists
3. domain specific word/phrase lists, (I'm not sure if this is based on category, opt in by including a template or both) see https://zh.wikipedia.org/wiki/Category:%E5%85%AC%E5%85%B1%E8... (I can't read Chinese - figured it out with Google Translate)
4. rules which apply for a whole article, see https://zh.wikipedia.org/wiki/Help:%E4%B8%AD%E6%96%87%E7%BB%...
5. rules which apply for a single word, see previous link
The whole thing is explained here: https://zh.wikipedia.org/wiki/Help:%E4%B8%AD%E6%96%87%E7%BB%...
The last 3 points address level 4 of Chinese character conversion mentioned in this article: http://www.cjk.org/cjk/c2c/c2cbasis.htm
I think OpenCC only implements level 1 and 2. I've looked at the source code to see that OpenCC gets "words" by using greedy longest prefix matching rather than fancier "Chinese word segmentation" -- I would guess MediaWiki does the same.
Anyway IIRC (and as the help page confirms) there are multiple conversion layers: letter-by-letter conversion tables (provided by MediaWiki itself), customizable word-by-word conversion tables [1] and special markup `-{...}-` for explicit variant selection [2].
[1] https://zh.m.wikipedia.org/wiki/MediaWiki:Conversiontable/zh... etc. You can also put them into the article itself, allowing domain-specific or article-specific conversion table.
[2] Mentioned under the heading "控制自动转换的代碼"; also can be used to turn off the wrong automatic translation.