Flame cutting is when the flame or pressure or hot gases released in the barrel/cylinder gap in a revolver actually cut a groove in the top strap. It produces a fine line, actually cuts into the top strap right over the barrel/cylinder gap.
Early 1900s Colts had a dimple cut into the top strap to alleviate this. This does nothing to alleviate it IMO. It just conceals the issue and the top strap comes from the factory weaker at that point. There are alloy frame revolvers that have a steel shield in the top strap where flame cutting would occur. More on that later.
It is most common with magnum (357,41, and 44) and all those super magnums out there (454, 480, 500). Now I'm not that familiar with those super magnums. Flame cutting is very common on S&W K frame 357s. It usually reaches a point and stops. Every S&W K frame 357 that has shot some magnums has it that I've ever seen. Most Colts, including Pythons have it. I have never seen it on a Taurus. The only Ruger I've seen it on was a Blackhawk in 357 Maximum. Never on any other frame style or caliber Ruger. Not saying it doesn't happen just saying I've never seen it. I've seen a lot of revolvers in my time.
When a revolver "kabooms" usually the cylinder blows up then the front (barrel end) of the top strap. It seems to me anything that weakens the top strap, even if it only goes so far, is not a good idea.
The tighter the barrel/cylinder gap the more pronounced it gets. Like I said it usually reaches a point and stops. I had a "pinned and recessed" (I think people make too much of that) Smith Model 19 I bought new in 1974 and used mostly for PPC competition and shot mostly wadcutters. I did put less than 1000 magnums through it and the flame cutting looked like someone had run a hacksaw through the barrel/cylinder gap. You could see the flame cutting looking at the side of the top strap. That's after about 5 or 6 years. No lifetime warranty then. I got rid of it.
While it's kind of an accepted thing with 357s my attitude is its avoidable with proper design. I don't mean just putting extra steel there.
Alloy frame revolvers? I said I'd get back to them. As I said I've seen that extra piece if steel that's supposed to prevent or minimize flame cutting with +P 38s. I've also seen people get alloy Smith J frames converted to 9mm parabellum. A friend has a steel J frame Smith that came from the factory as a 9mm. Looks and runs fine. However converting an alloy frame designed for 20,000 psi (38 spl) to take a 35,000 psi (9mm) cartridge seems like not too good an idea in my book. People who've had this done say the gun runs fine. I'd like them to let me know how the gun is running after 8-10,000 rounds like my 70s vintage Model 60 that has had zero parts replaced and timing is fine. That's at least 250 rds a year of +P for qualification for 30 years plus a few thousand more. No flame cutting either.
I don't carry +P in a J frame anymore. I carry factory wadcutters. Once you've put an entry and exit hole in the target any extra power just wasted energy and goes downrange. You can put that entry and exit in a target with a wadcutter.
I realize I more than answered your question but as a truly great man told me once "knowledge is not power".
The only stupid question is the one you don't ask.
Hope this helps.