Board Thread:Support Requests - Community Management/@comment-37124891-20200703113151/@comment-26611127-20200703125823

I don't believe you are allowed to prevent editors from adding categories to article pages. That may go against the customization policy, but you can for a more clear answer.

Regarding category names, yes you can rename (move) categories. You will have to go to the category page itself and use the "Move" option in the editing drop-down menu at the top right of the page. However, when moving a category, only the category page will be moved and any pages in the old category will not be re-categorized into the new one.

That being said, there is a script from the Dev Wiki that allows you to rename a category and automatically re-categorize pages into the renamed category.
 * See: w:c:dev:CategoryRenameAuto-update