Unless I’m missing something this seems trivial to test. Just test blood sugar before and after drinking a diet soda. If bloods sugar goes down then the sweetener likely caused a release of insulin. If it doesn’t change then it didn’t.
It seems petty far-fetched. If artificial sweeteners caused a runaway insulin spike then I would expect them to cause a lot of cases of diabetic shock.
And the joke is that Lemmy users are much further left than that.