This has been mentioned several times on the French WP, last time here: simple html formatting usually used in {{DISPLAYTITLE}} for article titles should be usable for Wikidata labels. For instance a superscript should have some way to be entered in the Wikidata interface, displayed as the title of the item and in its occurrences in other items, and passed to Wikipedia for display ({{#property:}} or mw.wikibase.getEntity etc.) as <sup>.
The problem is all languages which use things such as a superscript in the standard writing of some terms, for instance in French the numbering for royalty and nobility starts "Ier" (feminine "Ire") with the "er" ('re') part in superscript. Streets called "rue François Ier" always have a superscript "er" on the street sign and there is no other way to write it in French, "Ier" without a superscript would look like a non-existing name or word "ier". There have been isolated attempts to use for Wikidata labels the special Unicode characters for (phonetic) superscripts and even for (math) italics, but they are difficult to access and anyway their rendering is bad, since for instance the phonetic superscript series comes in several parts introduced in Unicode at different times and most navigators and systems use fonts that show some differences, like the superscript e and r not positioned at the same height., so this is not a solution.