I played in the 2-5 100-300 game at a local casino and after a few hours a better player sat down on my right and I am familiar with him. He is much much better than your normal player in the game. He understands hand reading and can thin value bet. he is also a bit of a LAG in late position.
I noticed after a while many times he would not cover his cards with his left hand as he look at them with his right. So I just waited and looked along with him. I see absolutely no reason to tell a player I can see their cards this is their responsibility and if they decided to give me the option I will take it. So I noticed hands like A5 os he would raise in lp and even once he slowplayed KK versus two short stacks.
I wondered that If I know what someone has you can play perfect against them. Would you just three bet their mediocre hands 100% of the time? Would this get so obvious that they might figure out you can see their whole cards? Or would it be better to get into a situation where you have a great implied hand against them and go for their whole stack?
I decided that if he did this last night he is probably doing this all the time and I would now have a strategy to try and stack him with an implied odds hand against a big hand of his. Rather than take the risk of winning a bunch of small pots and him wondering how it is I know exactly what he had. Too bad I was card dead and the one hand I did have against him he turned a draw and rivered top pair so I had to abandon. He never knew because I just mucked my hand.