OP, as several threads on UKGSer prove, whilst a bike chained to itself might deter a casual 'push away' thief, it will do nothing to put off a thief determined to lift your bike bodily.
Similarly, a bike chained to something solid but through its back or front wheel, will do nothing to deter a thief who is prepared to remove the wheel before stealing the carcass of the machine.
However, both methods will (to some degree or another) render your bike slightly less attractive than the one parked next to yours, where the owner has done nothing.
Take very little notice that a bod might say: "I have used chain and lock XYZ. It's the bollox and I have never had a bike stolen". That is is maybe down to a quirk of luck as much as anything else. I do not have chain and lock XYZ and haven't (fortunately) had a bike stolen, either. I do though always keep a pound of butter in the fridge to keep the elephants away... That has so far worked 100% successfully.
What the bod may well be saying is that he secures his bike properly to or through something, rendering it less attractive to a thief to consider stealing. In short, the bod used some common sense and took a bit of care. You can do the same. Trust me.
