As good of an idea as it may or may not be to remove this feature from the code 
base, actually doing so would be crossing a boundary that we have not 
previously been willing to do except under extraordinary duress. The nature of 
bitcoin is such that we do not know and cannot know what transactions exist out 
there pre-signed and making use of these features.

It may be a good idea to make these features non standard to further discourage 
their use, but I object to doing so with the justification of eventually 
disabling them for all transactions. Taking that step has the potential of 
destroying value and is something that we have only done in the past either 
because we didn’t understand forks and best practices very well, or because the 
features (now disabled) were fundamentally insecure and resulted in other 
people’s coins being vulnerable. This latter concern does not apply here as far 
as I’m aware.

> On Nov 15, 2017, at 8:02 AM, Johnson Lau via bitcoin-dev 
> <bitcoin-dev@lists.linuxfoundation.org> wrote:
> 
> In https://github.com/bitcoin/bitcoin/pull/11423 I propose to make 
> OP_CODESEPARATOR and FindAndDelete in non-segwit scripts non-standard
> 
> I think FindAndDelete() is one of the most useless and complicated functions 
> in the script language. It is omitted from segwit (BIP143), but we still need 
> to support it in non-segwit scripts. Actually, FindAndDelete() would only be 
> triggered in some weird edge cases like using out-of-range SIGHASH_SINGLE.
> 
> Non-segwit scripts also use a FindAndDelete()-like function to remove 
> OP_CODESEPARATOR from scriptCode. Note that in BIP143, only executed 
> OP_CODESEPARATOR are removed so it doesn’t have the FindAndDelete()-like 
> function. OP_CODESEPARATOR in segwit scripts are useful for Tumblebit so it 
> is not disabled in this proposal
> 
> By disabling both, it guarantees that scriptCode serialized inside 
> SignatureHash() must be constant
> 
> If we use a softfork to remove FindAndDelete() and OP_CODESEPARATOR from 
> non-segwit scripts, we could completely remove FindAndDelete() from the 
> consensus code later by whitelisting all blocks before the softfork block. 
> The first step is to make them non-standard in the next release.
> 
> 
>  
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