It appears to still be possible to use spectacle shortcuts and functions on a fullscreen or split view application's window. Which causes adverse effects and weird bugs.

Known issue for fullscreen mode (see #206). I'll close that issue out in favor of this issue.
I won't be using 10.11 for quite some time so unfortunately this is not likely to be fixed anytime soon.
Do you have any updates on this?
Will it be possible to move fullscreen apps to another monitor anytime soon? It is quite buggy at this point and does not move the app to another monitor if the app is in full screen.
El Capitan 10.11.5
Spectacle 1.0.6
Accidentally using a shortcut (e.g. move to upper half) in a fullscreen app seems to totally break Spectacle for a while.
El Cap 10.11.6, Spectacle 1.0.6
+1 I would love to see this fixed.
Quick update here. I've spent a bit of time looking into this issue. My original fix introduced a regression (see #455) so it had to be reverted. I just haven't had the time to find a reliable way to detect if a window is in fullscreen mode or not.
Most helpful comment
+1 I would love to see this fixed.