Trevor,
No, the error is yours and mine (I did say I've been wrong before

), not Wang's.
When I re-read your original post you quoted Wang as saying "the sum of the forces to the
left (left indicating the positive direction)...". The statement that positive is to the right was your own, and I did not pick up the inconsistency until just now.
I have also just picked up an error in my previous post, where I said draw the shear force "to the right at the top of the column gap, and to the left at the bottom". That would be the wrong way if clockwise shear were positive.
IF Wang's example is for sway to the right, and IF he is summing forces to the left as positive, and IF the terms for applied load to the right and shears in the lower columns have the same sign, then I have to conclude that he really treats
anti-clockwise shear (____|----) as positive.
IF that is correct, then the argument goes like this - For anticlock positive, you should draw +shear to the right at the top, and to the left at the bottom of each gap (just draw a column sheared anticlockwise with the bottom to the right of the top to see that). So (entirely due to an inspired error on my own part) your/our sketch is correct as drawn, with H9 etc to the right at the top of each gap, and to the left at the bottom. (Note that the equation of horizontal equilibrium would not change even if you had sway to the left – the direction of positive H9 etc is solely dependent on the sign convention for shear, and you draw the
variable H9 as I have indicated, even though its
value could be positive or negative).
Now sum the forces to the LEFT as positive, and I think you/I have it. At least I do hope so - even
I am beginning to lose sleep now.