Copied from Pau's specifications:
*'''Surface languages used in content.''' Articles contain content in different languages (e.g., an article about a Russian city will have the name in Russian even on the english wikipedia). Those languages indicate a special connection between the topic and the language. This may not be a language the user understands (so this criteria should not be a priority) but it may be a good option if there are remaining slots in the initial list of languages.
Example:
- I visit https://en.wikipedia.org/wiki/Leo_Tolstoy with compact interlanguage linbks enabled
- The page contains <b>Lev Nikolayevich Tolstoy</b> (<a href="/wiki/Russian_language" title="Russian language">Russian</a>: <span lang="ru">Лев Никола́евич Толсто́й</span>
- Whatever interface language and other conditions apply to me, the interwiki to "ru" is displayed.
As long as we limit it to 1-2 languages per page this should be a rather effective trick in the lucky (but important) cases where it applies, but it depends how efficient it is to scan the whole page like that.