Much of that particular response was in response to his claim that "if someone, from say, diamond tier, going trying to climb, that they would even have a freggin hard time climbing", which is provably false, since as you say, they have diamond skill and knowledge, and so they pretty much can hard carry most games (I wouldn't say every game).
Certainly the closer you are to your 'true' elo, the slower your climb, and really that's going to be true everywhere on the ladder. When you're within 1 division of your 'true' elo, whether that's a bronze 1 who deserves silver 5 or a plat 3 who deserves plat 2, then their long run win rate at that elo might only be like 50.5% or something only barely better than 50%, but if you are better than your current elo, you will bias the odds upwards from 50%. A challenger smurf in bronze may well be able to bias the odds up from 50% to 95%, while a plat might only manage 60% and silvers only like 53%, but in each case they will be able to pull more than their weight and drag the derps to victory more often than not.
Again, it's not a case of hard carrying every game, and certainly there will be some unwinnable ones as your teammates all feed their (questionably existent) brains out, but just a matter of statistics. 5 potential derps on their team, and 4 on yours, so on average you will net gain, it's just a matter of playing enough matches for statistics to pan out, and never getting frustrated/tilted to the point where you actually are dragging down your team.
