Luke,
There is nothing stopping you planning to fly in icing conditions, ie ATC won't ask 'confirm you want 8000 as it is above the freezing level?'.
Maybe I misunderstood but wasn't he saying that nobody will stop you from doing it at the time - ie ATC won't tell you not to - not that it isn't against the regs (which it clearly is) or that you won't be busted subsequently?
(Edit to fix up the formatting)