I was just thinking of someone who'd deliberately uploaded themselves and wasn't restricted - clearly suicide would be possible for them.

That is not self-evident to me at all. If you don't control the hardware (and the backups), how exactly would that work? As a parallel, imagine youself as sole mind, without a body. How will your sole mind kill itself?

And where there's information flow, control is surely ultimately possible?

Huh? Of course not. Information is information and control is control. Don't forget that as you accumulate infomation, so do your jailers.