core devs are being too hard-assed about it in my opinion 
we don't sign a message from an address. we sign a message using the private key just like we sign anything else including transactions with that private key. and the standard is already there (add a fixed string at the beginning -> double SHA256 hash -> sign -> encode with base64 with a recid).
that is what we have been doing all this time with legacy addresses and that is what Electrum continues to do with all types of addresses.
we don't sign a message from an address. we sign a message using the private key just like we sign anything else including transactions with that private key. and the standard is already there (add a fixed string at the beginning -> double SHA256 hash -> sign -> encode with base64 with a recid).
that is what we have been doing all this time with legacy addresses and that is what Electrum continues to do with all types of addresses.
Can you please elaborate what you mean by the devs being hard-assed? Are they debating another method to sign messages with a segwit key?