Selecting text in the rendered pane causes it to scroll

If I select text by clicking and dragging in the rendered pain (not the edit pane), it slowly scrolls the content, even if I stop moving the mouse, for as long as I'm holding down the mouse button. Version 0.6 (749)

Reproduce the issue by selecting text in the rendered pane of MacDown while holding the mouse button, and compare its behavior with the edit pane. Done means dragging to select rendered text no longer causes continued scrolling after the pointer stops moving.

Written by the indexing model from the issue text.