MediaWiki canonical URL form has "_" symbols instead of spaces. Yet, it seems WDQS stores them as %20, which makes them non-matching and harder to analyse.
select * where { ?sitelink schema:about wd:Q27. ?sitelink schema:inLanguage "en" . }
returns: <https://en.wikipedia.org/wiki/Republic%20of%20Ireland> expected: <https://en.wikipedia.org/wiki/Republic_of_Ireland>