First of all, this seems like a bug with Kate, or kde.
Has anyone looked for an existing bug report upstream? 
It also looks like Kate panics not finding a configuration file, instead of being cool and just create a new one.
OTOH it calms down after some actions. Even changing window size or position, informs/updates some file with new coordinates. This could create the missing file and save the day.
I’m on my phone, so can’t confirm my thoughts.
As already said, missing language/spelling languages is an old and not fatal issue.
Trying/testing if a bug exists in a freshly created user is always useful, even when it seems not logical. It confirms our assumptions. In this case, the 1st user (1000) is still a special user and random devs forget it’s not the only one in the system, or their testing is not extended to other users.