Platonides wrote:
Technically speaking "subst:" is a parser function, isn't it?
Not exactly a parser function. I would call it a /modifier/ for templates/parser functions.
Could I a least create an alias for it (by modifying magic words?) which is more meaningful for non English speakers?
You are not expected to translate it. You would need to modify includes/MagicWord.php *and* the literal comparison in includes/parser/Parser.php at braceSubstitution()
Thanks, Platonides, for those glimpses into the inner workings of MediaWiki. I have opted for your suggested solution of adding respective buttons to the WYSIWYG editor which IMO is better than tampering with core files ;-)