Further case in point on this....I once flew on a LUX-LHR-JFK-LCY/LHR-LUX itinerary where I booked the early flight to LCY and the late flight to LUX to take a meeting in the City in between. When I landed at LCY, the meeting had cancelled, and I had no desire to tramp across London to spend 5 hours waiting in the T1 lounge. I went to the LG desk at LCY and got on the next flight. Clearly there was no intend to break the COC, but how could BA know one case from the next?

Now, if you are doing it ten times a year, watch your back. Once or twice, though, is happenstance.

Furthermore, even if one does do this intentionally on occasion, they are still spending their money with BA. The first time BA takes action against that person, they likely lose the customer for life without recovering damages, even if they cancel a boatload of Avios. Not smart business, especially when the ex-EU fares are reasonable representations of the product value.