Wikimedia Language engineering/Developers

• Localisation
• Localisation/Tutorial
• Localization checks
• Manual:Language
• Writing systems
• Directionality support
• Date formats

Manuals having i18n documentation

• Manual:Interface
• Manual:Logging to Special:Log
• Manual:Messages API
• Some notes about small projects
• Help:System message
• Manual:Translating extensions
• Manual:Translations