I think the main issue is the blocking nature on anything that does not use the default zap, no? So if you comment, post or even just select a custom amount, the UI currently blocks until the payment failed or was successful.

If that's true, the toast isn't the problem afaict. As @k00b mentioned, it only exists so one can cancel pending payments.

You mean like showing a spinner instead of the lightning icon? Mhh, I see. Maybe we can do that instead of toasts and clicking the spinner would cancel the action. But that's a bigger lift, not sure if it's worth it if the toast is not the real problem.