The third message on https://en.wikipedia.org/wiki/Special:AllMessages is wikiLove.js, between the numbers and the messages starting with a. On the second and probably all other pages (https://en.wikipedia.org/w/index.php?title=Special:AllMessages&offset=Abusefilter-edit-builder-funcs-ccnorm) it is the first message. The same happens in de.wikipedia and probably other projects.
This has obviously something to do with the fact that in WikiLove/i18n/en.json (and the other localization files) WikiLove.js is defined with a capital letter.
Either at some place in core the first letter of a message key has to be transformed into lowercase, or (possible easier) that message should just be changed to wikiLove.js