Whilst DisplayFusion is active, middle-clicking a link in Chrome in order to open it in a new tab invokes a scrolling action first, causing the middle click to fire about 5 lines down the page. This does not occur when DisplayFusion is closed, but starts occurring again immediately when it is reopened.

Hah, that's embarrassing. Turns out that it's actually a subtle tilting of the mouse wheel to the left that causes it to occur; somehow I was activating that whilst DF was running and failing to whilst it wasn't. Which is doubly weird, really, as I tried it a few times with perfect repro. The screen with chrome is on my left, so it probably caused me to tilt the button left - closing DF would've occurred on another screen, which would've realigned it, until I went back to the left screen after starting it again.

Guess it's one of those bizarre unconscious things, apologies for the false report