The same way we check English, plus one more step. Every claim is sourced, every market page is built from that market's own operator and regulator information, and the build is checked mechanically for text that leaked in from the wrong language or the wrong script.
On one nine-domain network, that process turned up English fragments left in page furniture, wrong-script characters in a Traditional build, and one market that had been built as a near-copy of its neighbour. The automated checks passed all three; a person reading the pages found them, and the checks were extended afterwards so they would not recur. None of it is visible to a reviewer who does not read the language.