meld allows you to start an empty comparison and to paste content into it without saving.

I have experienced both cases where btrfs mounted read only for no good reason and cases where ext4 did not detect my storage medium had corrupted my data. I have chosen btrfs for data integrity but both options have upsides.

namei -om to check permission issues

Des poires.

I found ast-grep inconvenient to match several consecutive lines of python whereas comby handles this reasonably fine.