Translators who are experienced MediaWiki users sometimes use wiki syntax like [[]], {{}}, <ref> etc. because they don't find/seek alternative ways to achieve the same result (e.g. how to add a link inside the template translator, see T160251).
VisualEditor shows automatic warning or auto-converts this syntax, but CX doesn't.
See also:
- T138510: Make it possible to switch to wikitext editor from ContentTranslation's own editor before saving
- T105447: [Epic] replace plain contenteditable with VisualEditor in ContentTranslation
- T160251: Wikitext links in template translator are shown unparsed
- T152481: Add "wikitext recognition and transformation" function of VE to ContentTranslation tool