This one is poping up more and more often with trend of MMO's adding jumping puzzles but if you can't do plat-forming properly don't fucking do it. If a game doesn't really have exploration where you have to climb things then I don't mind invisible barriers (unless it's of the knee high fence that make you walk all the way over to the gate to enter the area variety) and geometry of the terrain on the borders not matching the visuals exactly. It's a little annoying but no big deal.
However if you are going to have platforiming sections and if you are going to have things hidden on rooftops and in hard to reach places then what is on your screen needs to match what is happening. There is nothing more annoying than having 5 different ways that it looks like you can reach something but 4 of them have invisible barriers preventing you going that way. It's especially annoying if you can't be sure which way is the correct way without looking up a guide since you could be suppose to be able to make a jump and be doing it wrong without knowing because the edge of the rock you're suppose to land on is higher or extends further than what is shown visually. Also dying because you jumped to an object you should be able to land on and just fell thru always pisses me off.
However if you are going to have platforiming sections and if you are going to have things hidden on rooftops and in hard to reach places then what is on your screen needs to match what is happening. There is nothing more annoying than having 5 different ways that it looks like you can reach something but 4 of them have invisible barriers preventing you going that way. It's especially annoying if you can't be sure which way is the correct way without looking up a guide since you could be suppose to be able to make a jump and be doing it wrong without knowing because the edge of the rock you're suppose to land on is higher or extends further than what is shown visually. Also dying because you jumped to an object you should be able to land on and just fell thru always pisses me off.