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Date: Tue, 31 Jan 2023 13:33:13 -1000
From: "David A. Harding" <dave@dtrt.org>
To: Greg Sanders <gsanders87@gmail.com>
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Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Reference example bech32m address for future
 segwit versions
Precedence: list

On 2023-01-31 04:30, Greg Sanders wrote:
> Hi David,
> 
> From practical experience, I think you'll find that most exchanges
> will not enable sends to future segwit versions,
> as from a risk perspective it's likely a mistake to send funds there.

Hi Greg!,

I thought the best practice[1] was that wallets would spend to the 
output indicated by any valid bech32m address.  You seem to implying 
that the best practice is the opposite: that wallets should only send to 
outputs they know can be secured (i.e., which are not currently 
anyone-can-spend).  The more restrictive approach seems kind of sad to 
me since any problem which can result in a user accidentally withdrawing 
to a future segwit version could even more easily result in them 
withdrawing to a witness program for which there is no solution (i.e., 
no key or script is known to spend).

If it is a best practice, then I think there's a benefit to being able 
to test it even when other people's proprietary software is involved.  A 
wallet or service likely to follow that best practice may be more likely 
to follow other best practices which cannot be as easily tested for.  
But, if it's going to be tested, I want the testing to use the address 
least likely to cause problems for protocol developers in the future.  
Do you (and others on this list) have any reason to believe OP_16 
OP_PUSH2 0000 would be a problematic script, or can you think of a 
better script?

Thanks!,

-Dave

[1] BIP350, emphasis in original: "[...] we emphatically recommend [...] 
ensuring that your implementation supports sending to v1 **and higher 
versions.**"