I discovered at some point while playing that it is possible to make your character turn 360 degrees while kneeling but it still appears to other players that you are turning only 90 degrees.
You can do this by quickly tapping "a" or "d" once (or whichever keys you use to strafe left and right) while kneeling. If you do it fast enough that your character doesn't move and stand up, you will be able to rotate 360 degrees. Several people have been able to repeat this without fail.
Attached are images showing that you aim normally, what it looks like to other players, and a gif of me being shot while it clearly doesn't look like he's aiming at me.
P.S. Another bug I found that's somewhat related (they can definitely be paired and devastating) is in the attic of the house on Nicodemus Hill. If you kneel in the corners by the windows (those walls are fake and can be walked through and shot through) you can move a small distance left and right while still kneeling. I'm not sure if that requires it's own thread as well. If it does, I'll make one showing it happen.
EDIT: the .gif file wasn't uploading properly so here's the video:
https://gyazo.com/e55b5785b97f26b69f8c04f91bdecc54