It feels like having a predefined list of keys that are ignored is a "hack". Would a better solution be to simply wait until none of the _trigger_ keys were pressed?
E.g. if the sequence was "Ctrl" + "F8" then it would just ensure that neither Ctrl nor F8 were pressed.
>If, for example, “shift” is held when it’s typing, letters will be capitalised
This applies regardless of whether Shift was part of the hotkey or not. ie in your case where the hotkey is Ctrl-F8, if Shift is held down while you press Ctrl-F8, then the xdotool spawned by hk will end up typing uppercase.
E.g. if the sequence was "Ctrl" + "F8" then it would just ensure that neither Ctrl nor F8 were pressed.