This page summarises some key I18N issues - it's not comprehensive, but it's very useful to have a list of the most significant known I18N issues so feel free to add them as they are reported in Codev or Support.
SomeChineseCharactersBreakWikiLinks - Links to TWiki pages using certain GB2312 characters do not work - fix is to use a safe character set. The same problem exists with Shift-JIS, Big5 and most other East Asian character sets, apart from EUC variants and UTF-8. Unsafe character sets are now excluded in TWiki 4.0 - included here as warning not to use these character sets. UTF-8 is generally best option for East Asian TWiki sites.