Unless you were on a pool and noticed you were 'down on your luck' for an insane amount of time, you would not notice and even so could never be conclusively proven either. Sneaky...

Has there been any known cases with MRR or NH?

Thanks for this pool, by the way. I notice that the way you have it set up for insanely fast block changes and the code quality is why I will keep my small miners here. I also saw you paid out a block that was missed due to a fault with this pool a while back, I wouldn't solo mine anywhere else, not even on my own node as this seems the most trustworthy place to put my miners knowing that if I found a block it only has a low chance of getting orphaned... Well worth the fee that is deducted from the found block.