Drag and drop of text within contenteditable does not work as expected

Phenomenon

Dragging selected text within a contenteditable region to move it to a different position does not work consistently. Sometimes the text is copied instead of moved, or the drop target is not where the mouse pointer indicates.

Reproduction example

1. Create a contenteditable div with multiple paragraphs.
2. Select a paragraph of text.
3. Drag it to a different position within the same contenteditable region.
4. Observe the result.

Observed behavior

• In Chrome on macOS, dragging text sometimes results in copying instead of moving.
• The drop position may not match the visual indicator.
• The original selection may remain visible after the drop.

Expected behavior

• Dragging selected text should move it to the drop position.
• The original text should be removed from its source location.
• The caret should be positioned at the drop location.