The mechanism you're describing sounds backwards to how normal competition works, so it's worth digging into what Ofgem is actually proposing versus what headlines suggest. If suppliers had to pay each other for winning customers, that would theoretically make aggressive discounting less attractive - the logic being it reduces "poaching" and encourages stability. But yeah, you've spotted the obvious flaw: companies competing less hard means less pressure on prices, which benefits them more than customers.
The real impact depends on whether this is framed as a fee to prevent predatory practices (like unsustainable loss-leading) or just a blanket penalty on winning market share. One protects weaker suppliers; the other just kills incentive to offer better deals. The tricky part is that energy markets are already weird - fixed-term contracts, switching costs, and supplier failures in 2021-2022 showed the system has genuine fragility. A policy that sounds like it's protecting stability might actually just entrench higher margins.
Practical thing most people don't think about: start tracking what your actual unit rates are, not just the headline price. Suppliers bury the real per-kWh cost in different ways, and when competition gets softer, that's where the squeeze happens. If you're on a fixed deal now, lock it in before any rule changes settle, because once suppliers know penalties are coming for cutting rates aggressively, new fixed offers tend to get quietly less competitive. Keep a spreadsheet of what you're paying per unit - sounds tedious, but when you do switch, that number matters far more than the total bill promise they advertise.