My Dell Latitude E7440 follows description and I believe same is true for most of the users. I have to start movement at least diagonally, once it catches further direction does not matter.

It produces no output when running `libinput debug-events`. I've recompiled my version with 0% just to check.

            /* palm edges are 8% of the width on each side */
    -       mm.x = min(8, width * 0.00);
    +       mm.x = min(8, width * 0.08);
            edges = evdev_device_mm_to_units(device, &mm);
            tp->palm.left_edge = edges.x;
     
    -       mm.x = width - min(8, width * 0.00);
    +       mm.x = width - min(8, width * 0.08);
            edges = evdev_device_mm_to_units(device, &mm);
            tp->palm.right_edge = edges.x;

    $ yay -G libinput
    $ cd libinput
    $ makepkg -so
    ==> Verifying source file signatures with gpg...
        libinput-1.16.4.tar.xz ... FAILED (unknown public key E23B7E70B467F0BF)
    ==> ERROR: One or more PGP signatures could not be verified!
    $ gpg --recv-key E23B7E70B467F0BF
    $ makepkg -so
    $ vim src/libinput-1.16.4/src/evdev-mt-touchpad.c 
    $ makepkg -fei