"You can Spacewalk between any two Modules nearest one another, provided you can draw a straight, or diagonal, line between them and they’re separated by empty space. This gap may be part of the ship’s original design or caused by the ship breaking apart."
You can spacewalk from one corner to another as long as you can draw a straight line with empty space between them. Doesn't have to be broken apart. (And Threats don't spacewalk (see below in one of the comments from the creator), so there might be a reason to take that risk once in a while.)