Previously a kata would become locked once 500+ successful solutions had been submitted. This was done to try to minimize authors from making changes that would invalidate a large number of solutions on popular kata.
The new approach is to only lock the test cases from any edits. The rest of the kata remains editable so that things like typos, poorly worded instructions & missing example test cases can still be added to popular kata.
When you go to edit your kata, you will notice a lock icon next within the test cases tab.