The answer should be: alphabetically.
Currently, I have a page starting with 'A' appearing in the 'S' section of the category overview page.
Screenshot: https://i.sstatic.net/pKide.jpg
I have a small Wiki running for my team:
and this is the first time I have ever spotted something like this.
The 'Abana' page refuses to appear in the 'A' section. I've moved/changed the name of the page and it still appears in 'S'section regardless:
Screenshot: https://i.sstatic.net/DpM8V.jpg
New pages created after the 'Abana' page appear in the right section of the alphabet, and they do so in all categories on the wiki.
The page itself contains very little:
ASANA useful plugins
Find the Alfred workflow / quick entry instructions [https://asana.com/apps/alfred here]
[[Category:ST ORG IT|ST_ORG_IT]]
I don't know enough about debugging MediaWiki installs to know where to start looking to fix this.
My configs are fairly standard, and there aren't any that mess with the categories:
I'd really like to get my letters back in the right order; whilst the order being wrong isn't the end of the world, I wonder if it is indicative of something more serious.
Any pointers greatly appreciated!
[[Category:ST ORG IT|ST_ORG_IT]] tells MediaWiki to put it into the ST ORG IT category with a sort key of ST ORG IT. You'll want [[Category:ST ORG IT]].