With JJ you can even override the ref spec of what should be considered a mutable commit. Feel free to set it to all commits and JJ will not allow you to mutate anything unless you pass the --ignore-mutable flag.

For example, I've configured it for me to make any commit by anyone else mutable regardless of branch:

    [revset-aliases]
    # To always consider changes by others immutable:
    "immutable_heads()" = "builtin_immutable_heads() | (trunk().. & ~mine())"