I propose to add highlighting of selected words and line modification indicators. Former appeared in KDE 4.6, latter in KDE 4.8. At the same time, it would be good if the area over the indicators (for the aims of mouse Drag&Drop) was understood still as the first column of the text, in contrast to an annoying KDE 4 behavior (in terms of mouse precise navigation), where dropping the text just outside of the very thin first-column area creates a new file.
Here are the previews of these features from Kate 4.x
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