Changing component of a bug report automatically checks 'Reset Assignee to default' and 'Reset QA Contact to default'. When you don't uncheck it (obvious) the fields will be reseted.
Quite annoying when you are in the QA field, and someone changes the component without unchecking it... when you don't place yourself back in that field, you'll not get any information anymore (unless you always place yourself in the CC field too).
@Joel: I think you also experience this :)?
(In reply to comment #0)
> Changing component of a bug report automatically checks 'Reset Assignee to
> default' and 'Reset QA Contact to default'.
That's only true if the current assignee or QA contact is the default one. If it's set to someone else, the field is not reset.
ticket moved to redmine https://redmine.documentfoundation.org/issues/1528