Found by openQA: https://openqa.opensuse.org/tests/2426945#step/kate/18 The icons on the left look a bit weird (in particular, too big) and the lone braces on the right don't look like they're intended to be like that either. This is at the first start of kate, so using vanilla configuration.
This was a recent change: https://invent.kde.org/utilities/kate/-/merge_requests/763 Can be switched to older style from "Configure Kate ... -> Behavior"