I know you're not talking to me, but I think I understand now: the NOP really is something that invalidates a tx in the context of relaying and mining it because the assumption is that this NOP isn't there for fun, but it really is not a NOP for the author of the tx or the miner of it. I just don't know the new meaning of the NOP so I don't touch the tx with a ten foot pole... who knows wether that script returns true or false?

On the other hand a NOP in a tx in a block already mined by someone else is not offensive: the assumption is that it was assigned some meaning I don't yet know about and the block was mined by a miner that *does* know about that new meanig and he has verified the tx' validity.