You can bind actions to contain modifier keys. Eg. Control+G, Control+A, etc.
Which should indicate that if you press A, and you're holding control, that actions will be activated.

However, that's not the case.

Instead, what seems to happen is that when you touch a modifier key, like control, the game sets a flag, and a timeout of like 250 ms.

If you then within that time hit any other key, it'll combine them as if you did Modifier+Key, even though you didn't.

This causes great grief, as you have to delay all your key presses.

To clarify: If an action is bound to eg. Control+A (Side step left), the game will trigger that action if you press control, release control, then hit A (even though you're no longer holding control).

This means, that if you eg. press Control+G to switch current grenade type, then press G to throw, what happens instead is that you switch current grenade type twice.