Gregory Maxwell explains that ordinary P2WPKH transactions have less weight than P2PHK, while SegWit transactions like P2WSH and P2WSH/P2SH cost more space compared to P2SH. Alberto De Luigi argues that exchanges have no incentive to adopt SegWit as it increases blockchain weight without saving space or offering cheaper fees. Bech32, on the other hand, can save up to 22% of space and could help scale Bitcoin with coordination among wallets.The conversation between Alberto De Luigi and Mark Friedenbach focuses on the adoption of SegWit and the concerns surrounding it. Alberto questions the usability of bech32 addresses and their recognition by certain software. Mark clarifies that the recipient has control over which payment script is used, and bech32 addresses offer better security guarantees or lower fees. Alberto also raises concerns about the increased block weight and lack of incentives for exchanges to adopt SegWit. He suggests a hard fork upgrade to bech32 along with a 2x block size increase to promote SegWit adoption and test the Lightning Network (LN). The conversation emphasizes the need for consensus among the community for coordinated upgrades.In the email thread on the bitcoin-dev mailing list, Alberto asks about the transaction size of SegWit. Mark explains that addresses are a user-interface issue and changing them does not constitute a fork in the bitcoin protocol. He highlights the benefits of bech32 addresses and the potential to reduce fees and improve security. Alberto expresses concerns about exchanges' reluctance to adopt SegWit due to increased block weight and lack of incentives. He suggests a hard fork upgrade to bech32 alongside a block size increase to enforce adoption. The email includes links to resources discussing the benefits and costs of SegWit adoption and different address formats.The email exchange also discusses the technical aspects of SegWit adoption. Mark explains that addresses are a UI convention and do not affect the bitcoin protocol. He suggests that bech32 addresses offer better security or lower fees compared to older address formats. Alberto raises concerns about SegWit adoption by exchanges, particularly regarding transactions with multiple outputs. While SegWit can save space and reduce fees in some cases, it may not be beneficial for all transaction types. Alberto suggests a coordinated upgrade to bech32 combined with a block size increase as a solution to promote SegWit adoption. The email thread includes links to further information on the benefits and costs of SegWit adoption and different address formats.Overall, the discussions highlight the complexity of SegWit adoption and the need for consensus among the Bitcoin community. The use of bech32 addresses is seen as a potential solution to improve scalability and promote SegWit adoption, but compatibility issues and the need for coordinated upgrades pose challenges. The provided links offer additional resources on the technical aspects and benefits of SegWit adoption.