. . .
A miner of bitcoins, or any derivative thereof that has not been made to do otherwise, can willfully exclude the "null data" type of transaction from the blocks he or she mines and still have the blocks accepted.
I personally don't use null codes when encoding data into the blockchain. They may be the right way to go eventually with enough development support, but as you bring up for now it is actually best if one doesn't depend on any unusual transaction behaviors like null codes to encode data.
OP_RETURN OP_[bytes of data] [data]
It doesn't matter how you do it, if it's unique enough, it can be filtered out.
Note that the transaction below contains the entire Bill of Rights encoded into the blockchain using only the normal methods of transaction formation. How would you filter it out?
http://bit-comm.appspot.com/packet/d71e39e493a1eaa4eb7c39e5a34ceb002649315321b3cc6e9ea25fcc765de1c3?expanded=true. . .
This software features
Bitcoin hard-fork requests such as the
exclusive use of both pay-to-script-hash within all (non-data) transaction outputs and the exclusive use of fixed-width, 64-bit unsigned integers in storing block times. Writcoin, the protocol wherefor this software is a client, utilizes a Proof-of-Work based on transaction tree Merkle roots and short (here, ten second) block times called Proof-of-Wait, requires coinbase transactions to not have any inputs and to only have one, unspendable output, permits coinbase transactions to originate outside blocks, and permits deficit spending (that is to say, it permits transactions total output value to exceed its total input value). Great Empire Coin (GEC) is the state money that is exchanged through Writcoin. G.E. coins are the state money of
Great Empire of Earth, are divisible into cents and mills, and have denominations of mega-, terra-, and exacoins.
. . .
"[E]xclusive use of . . . pay-to-script-hash [P2SH] within all . . . transaction outputs" should do it.