There is currently a proposal to make {{!}} a magic word that directly outputs |, the pipe character, rather than calling Template:!. If your wiki currently has Template:! set up to output a pipe, or if it doesn't have a template called Template:!, then this change doesn't affect you. All of the Wikimedia Foundation's wikis that have Template:! are currently using it for this purpose, some with a few minor issues:
* https://bg.wiktionary.org/ has had their Template:! tagged for speedy deletion (though not deleted) since 2012, although a pipe was its original content. This currently renders {{!}} non-functional on this wiki, and this change will cause it to become functional again. * https://fi.wikiquote.org/, https://mk.wikibooks.org/, and https://mk.wikisource.org/ all have extra whitespace alongside the pipe character in Template:!, which is likely unintentional. This change will cause the extra whitespace to not be used when {{!}} is used.
As of now, no WMF wikis need to make any further changes to prevent this magic word from breaking anything. Any non-WMF wikis using {{!}} to produce something other than a pipe character will have to move Template:! to a new name and update all transclusions to point to the new name directly. AutoWikiBrowser can be used to assist with this process if necessary. If any of these wikis don't do this before upgrading to 1.24, pages using {{!}} will render incorrectly until they do so.
See https://gerrit.wikimedia.org/r/#/c/136234/ for more details about this proposed change.
Regards,
Jackmcbarn