Good Topic
This is a good topic. A very obvious chasing of hands is when your are doing chi sau with a student, you disengage and do a wide slow obvious hook punch (for training purposes) and that student goes outside of his body boundary to block the hit rather than to just hit straight forward upon loss of contact as the Wing Chun maxim suggests. If you just hold that hook punch out there so the student can't even contact it, then he realizes that it was a waste to try to connect with the hooking punch rather than to just hit straight forward.
We use the suggestion that whatever attack comes your initial response should be to strike the opponent and not think about blocking or deflecting incoming hit. Of course if the counter strike is executed wisely then you will also position yourself away from the opponent's flight path or you will also have a barrier (Wu sau or Tan sau or Pak sau) there for the incoming strike at the same time.
The danger of interpreting not chasing hands as totally ignoring the opponents hands and just going for the hit is that you might get hit or that all Wing Chun comes down to two people chain punching each other to death in a wild flurry of action where both sides are getting hit. I think to prevent this kind of thing in fencing they put in a rule that you must engage the blade of the incoming strike first and then you can counter hit. But I am not a fencer so I could be wrong. Depending on the circumstance of use and the relative skill of the opponent, sometimes you don't want to hit the guy and just control (teacher vs elementary school student for example or drunk relative at a Christmas party).
In an effort of trying to prevent from getting hit, many students like to try to grab the hand coming in (like Aikido). Someone with quick reflexes could take advantage of this and when the hand is suddenly not there you got big problems. You have just wasted a movement trying to catch a bird by the tail as they say in Tai Chi but it has taken flight and you don't know where it went. MY Hung style teacher was very good at doing decptive "S" shaped strikes that looked like they were coming in at a certain angle, so that if you tried to block then suddenly the strike would end up coming around your block to hit you anyway. The instant you thought about blocking the strike would be elswhere.
The superior thing to do is to counter a strike with a strike without getting hit. But this isn't always possible. Sometimes you just have time to cover the space and the incoming strike connects with your limb somewhere maybe with the Bong sau and Wu sau combination or Bong sau and Tan sau combination (Kwun sau) leading to a grab and punch/chop or with a Pak sau movement leading to a punch or chop.
The blocks of some systems like in Hung style are often considered strikes because they are meant to destroy/damage/hurt the incoming limb like an anti-missile strike.
Some will feel this is chasing hands and some won't. Against inferior kickers it seems quite effective just to kick the incoming kick.
Victoria, British Columbia, Wing Chun