On second thought I am not so sure again. I kind of like the idea that in theory this reporter could be re-used for something else. E.g. you could do

>> reporter.format = Reporter::DefaultFormat

and the reporter would make use of the ReportFormatter again.
I am aware that this probably will never happen, but I like the idea of one, reconfigurable object even if that means that we pass some parameters to it that might not be used.

So I'd vote for leaving it like it is.:)