Commitment transactions are huge part of the penalty system Lightning enforces to make sure everyone plays nicely with one another, it make sure that if someone in the channel broadcasts an older transaction, thus trying to scam the other party, the commitment transaction will allow the first party access to the scamming party’s coins.

There were recently a few proposals to edit the commitment transaction, mainly the edits are about the format. Making the CLTV timeout symmetrical to avoid trying to pressure the peer into closing, making the remotepubkey BIP-32 styled and using the OP-TRUE style output to allow Child Pays For Parent fee dependancy.

Alejandro Ranchal Pedrosa and Tucci-Piergiovanni proposed a new BIP to extend OP_CSV¹ and/or OP_CLTV² to allow and interpret negative values.

The discussion that followed concluded that the BIP would be breaking a fundamental rule which is that valid transactions remain valid. This could lead to loss of funds when several transactions are made invalid.