I always thought it was a strategy to force somebody to sell.

Say you hold 1000 lots and Q to sell at RM5.00. That's the lowest price anybody wanted to sell. Somebody Q at RM4.90 but couldn't get. So, that guy "kacau" the RM5.00 Q by buying 1 lot which happens to be yours! You end up with a partial match of 999 lots PLUS you would need to pay the commision. If the Q doesn't go up, then it is either you keep the 999 lots and pay the commision or you are force to sell at a lower price i.e. RM 4.90.

That's what I think anyway. Don't listen to me as I'm just a noob....