If it's literally a table of strings, why on earth would anyone use ODF/OOXML? CSV is perfectly fine for editing in any functioning spreadsheet software, works reasonably well in version control (especially since a given commit won't touch multiple columns). In his case, he's using the XML format which Haxe will parse into compile-time-checked references right in his source code; sounds like a great reason to use this standardized(but Haxe-specific) XML format.