'tis a chrome/Firefox oddity. They're centred on Firefox.
Annoying, I know.
I have set up a number of categories and disabled some of them, it looks like this in admin panel.
But when creating a new post, user still can choose disabled categories!
Steps to reproduce:
Disabled category should disappear from everywhere, including categories list when creatign topic.
What is your git hash?
Git hash is 53af9ec2e806c25a2933ca8440e3f8d21e74bcd5
I just did a clean setup recently, maybe a week ago.
Can you post a screenshot of the settings page from one of the categories?
I made some fixes to the composer for disabled categories, will be available in next release. Thanks for reporting.