Short of making a new widget which inherits the built in widget, and overriding the method, no 
There is a trac ticket to include a login widget since theme compat is killing sidebar code, I took ownership of ticket, I’ll look through other widgets and make markup better add anything missing.
@paul,
Thanks for the suggestion, I just didnt want to deregister a widget and create exactly same one just because of two characters (:
@modemlooper
Thats great to hear (: It would make styling much easier if | would be wrapped by span for both Groups and Member widgets.
Thanks again