The prompt asks for [1][2] when a sentence rests on two sources, and raised
digits carry no separator of their own, so the pair was drawn as 12: one
number, with nothing to say where the first citation stopped and the second
began. Reported from a real answer, where two sources came out as one glom.
Markers are now matched as a run, so [1][2] and [1, 2] both arrive as raised
digits separated by a comma, and a run containing a number we were never shown
is left exactly as written. A newline still ends a run, so two lines of
citations never become one sentence.
The marker itself is raised too: [1] is drawn as a superscript link, which is
what a citation mark is, while the entry under the answer keeps the plain
number at baseline where a list is easier to scan.
adrianbonpin