System messages order in list field

[Joel Guillod]

I notice that the system messages order for list field differs  
depending on the hilited state of the clickline:

case 1: when clicking on a *unhilited* line:  mousedown ->  
selectionChanged -> mouseUp

case 2: when clicking on a *hilited* line: selectionChanged ->  
mousedown -> mouseUp

Is it a bug or a feature? Is there some explanations on the purpose  
for such a different order?

Joël