I found that when I intentionally desynced the client from the server and had the cube move only on the client, the client character could jump through the moving cube, but could not jump through the space where the client said the cube was.
When I jumped with the client on to the empty space where the server-side cube was, I suddenly saw my client character teleport to the client cube which was still moving beyond the map at that point. The server side saw the client character standing on the motionless cube. (see images below, the femme character is the server, the masc character outside the wall is the client).
My intuition is that, when jumping at the client side moving box, the client tried to stop my character’s movement, but the server then updated it so I had moved through / into the box. Similarly, the server detected that the client jumped onto the box, and I’m guessing that collision was communicated to the client, which updated to teleport the client character onto where it thinks the box is.
Note: Client-character couldn’t jump onto the client box, they fell through. Both characters can only jump on the server box location, and then appear on the client side wherever the client box is.
Thank you for coming to my KY talk.