There's a divergence of views regarding the incorporation of the CHECKSIGFROMSTACKVERIFY (CSFSV) opcode into pre-tapscript versions. Advocates for its inclusion argue that its compatibility with NOP forking warrants its addition, drawing parallels to how CHECKTEMPLATEVERIFY (CTV) functions as a NOP compatible upgrade. This alignment is believed to facilitate the use of Schnorr signatures in earlier script iterations, potentially broadening their applicability and flexibility. Conversely, some participants question the necessity and value of integrating CSFSV without a compelling or concrete benefit being demonstrated, much like the situation with bare CTV for older scripts. They suggest a more prudent allocation of the limited NOPs, especially considering the implications for extending Schnorr signature commitments to legacy scripts.

Further, the discussion extends to the proposition of adding CHECKSIGFROMSTACKADD (CSFSA), driven by the notion that script multisig could become a prevalent method for signature verification on stack data. The introduction of CSFSA is posited as a means to reduce the complexity and error-proneness of crafting script multisigs, potentially making them lighter in weight units (WU) per key. Although advancements in multisig technologies like MuSig2 and FROST may not position script multisig as the primary application for these opcodes, the argument for CSFSA rests on its ability to simplify the development of miniscript-based multisigs. By dedicating an OP_SUCCESS to CSFSA, the process of creating these script multisigs could be streamlined, enhancing efficiency and accuracy.

Brandon Black’s outreach for feedback on this matter reflects the open and collaborative ethos of Bitcoin protocol development. It showcases a willingness among the community to carefully consider and refine proposals based on collective insights. This approach ensures that any enhancements to the Bitcoin protocol are thoroughly vetted and agreed upon by a broad spectrum of contributors, with the aim of optimizing the functionality and security of the network.