Crewe and the aforementioned response to anyone who might merely creep over the yellow line despite the line being well back from the train and no indication that the person is going to place themselves in a position where they're too close to the train - there's more than a fair share of stations where if you tried to wait for everyone to be behind the line you'd never depart!
The issue at Crewe, especially on Platform 9, is down to staff there refusing to fight the root cause of the issue because it involves them moving.
They completely ignore the fact that pax alighting from a train on P9, are generally forced to cross the P6 yellow line because of the huge crowds that form and Crewe Station Staff' inability to sort out boarding pax. Crewe station staff think that it's perfectly ok for 150 odd people to all huddle next to the P9 buffers and then crowd around the first set of doors. This means in most cases, even people trying to get off the Chester shuttle have to shout, make passive aggressive gestures, or snide comments just to get silly people to shift out of the way (Pax boarding at Crewe P9 seem to lose all sense that for them to board the train, they might have to let people off). When off the train, because of the crowds (which won't move and the crowd generally getting wider and wider), alighting pax have to cross the P6 line to get anywhere as there is literally no other way to get off the platform.
The solution here is rather than scream at arriving passengers to get back behind the P6 yellow line, for Crewe staff to walk (god forbid) up to Platform 9 and strongly encourage departing passengers to spread out along the platform. You can have 5 car trains and yet I think I must be the only person seeing the other 4 carriages as almost everyone insists on boarding only the carriage (and specifically the doors) closest to the buffers. Even train crew struggle to get in and out of the cab because the crowds are endless and Crewe station refuses to tackle it. It's a complete and utter farce.
Then again, why walk up to Platform 9 and get people to use the full length of the platform so alighting passengers can alight from the train and safely exit the platform, when instead you can stand 100m away up Platform 6 (out of the way of most of the passengers, chat to colleagues and be closer to the staff room), and just scream at pax crossing the P6 yellow line. No brainer really.