App developers express a preference for Key/Value (K/V) syntax due to its widespread support across programming languages and frameworks, which facilitates parsing and binding. This format is favored because it provides explicit information about the payment type, making it easier for app developers to handle transactions effectively. The choice of address formats involves balancing compatibility with various systems and cost-effectiveness, reflecting a broader consensus on accommodating the receiver's comfort and technological requirements.

At Bitrefill, the transition to SegWit bech32 addresses for payments has been smooth, highlighting an industry move towards efficient and future-forward address formats. The possibility of integrating Taproot addresses as an option was also discussed, suggesting an ongoing exploration of leveraging technological advancements to optimize transaction costs and functionality. This reflects a careful consideration of evolving address formats, aiming to improve the payment experience while ensuring compatibility across different wallets.

Further discussions delve into optimizing URI parsing for Bitcoin payment addresses, proposing changes to BIP 21 to minimize ambiguity and enhance backward compatibility. The suggestion to place future address formats in query keys as optional payment instructions aims to clarify parsing processes, ensuring a single location for address type identification. This approach also encompasses handling bech32 or bech32m format addresses efficiently, advocating for a standardized method across Bitcoin and Lightning networks to accommodate new address types. The debate extends to the efficiency of incorporating K/V pairs for bech32(m) addresses within BIP21, weighing the redundancy against the complexity of parsing multiple addresses and parameters. Despite recognizing bech32(m) addresses' inherent key-value structure, the conversation acknowledges the importance of not relying solely on this format for future address types, suggesting a balance between simplification and flexibility in adopting new standards.

The optimization of QR code data representation for cryptocurrency transactions emerges as a focal point, discussing strategies to balance efficiency and compatibility. Introducing an optional dummy value in the data string represents a transitional solution aimed at reducing QR code size while maintaining interoperability with existing systems. However, concerns about the space savings versus potential drawbacks, such as parsing complexity and future-proofing of addresses, highlight the nuanced trade-offs involved in optimizing QR codes. The proposal underscores the importance of cautious innovation that does not compromise backward compatibility or limit future technological developments.

Expanding BIP21 to support split payments illustrates a proactive approach to evolving the Bitcoin ecosystem, proposing modifications to accommodate more complex transaction types. This includes allowing multiple payment destinations within a single transaction, enhancing BIP21's utility and flexibility. The discussion acknowledges current limitations and the necessity for wallet software updates, reflecting ongoing deliberations on improving payment protocols to meet emerging needs without compromising simplicity and security principles.

In summary, the conversations revolve around refining cryptocurrency transaction mechanisms through technological advancements and standardization efforts. These discussions highlight the community's commitment to optimizing payment experiences, addressing compatibility issues, and preparing for future developments in the cryptocurrency landscape.