You can see in the thread you linked by the disgraced Samourai developer 'PavelTheCoder' that he calls my suggestion to enable privacy features by default on Samourai wallet "a retarded change".
Samourai admits to collecting their users' xpubs, which contains full history of all their transactions (including coinjoins): https://twitter.com/SamouraiWallet/status/1647673165353549825Without these critical privacy features enabled, Samourai acts is a surveillance app. It's incredibly dystopian to believe that one company controls so much data.
1 - Both Samourai and Sparrow tell you the size of your change output prior to signing and broadcasting Tx0. If you don't want to create a change output of this size, then you go and edit your transaction. This is the expected behavior of any good wallet.
Tell me why you would you ever want to send an output to yourself that costs more in sats than it is worth.
2 - Tx0 clearly pays the coordinator, and this output is easily identified. The privacy of Whirlpool coinjoins does not depend on this fee payment being secret. It does not matter if you and I both pay to the same coordinator address - there is zero loss of privacy.
Apparently you are not aware of Samourai's statements regarding reuse of coordinator fee addresses:
https://stephanlivera.com/episode/150/Stephan Livera: Also. So recently there’s been this whole debacle around Wasabi wallet getting flagged. So essentially some users, so the two recent examples, which to my knowledge, are the third and fourth cases that I know of. So there was Catxolotl from Binance Singapore. And then the other guy was RonaldMcHodled. RonaldMcHodled was withdrawing from Paxos. And so it’s sparked up this whole debate about basically how easy is it to flag CoinJoin transactions. My perspective on it was, look, these are like an unforced error. Wasabi should not have had a fixed fee address. And in fairness to Wasabi they are now changing that, after a lot of debate and a lot of time on this topic.
Samourai Wallet: It doesn’t matter now though. The impact has already been made. There’s no going back from more than a year of address reuse. It’s tied into the architecture of the mixes now. So it’s very good that they finally changed that. But it really isn’t going to do all that much.