YouTube is painful when trying to read comments that are a number of 'pages ago'... that could be anything in terms of real time, depending on popularity, i.e. if dozens or hundreds, thousands are posted.
Trying to scroll back is agony. If a a commentator is posting more than a few, and perhaps the comments are attractive, the temptation is to click on the individual's profile to find out more... You might be awarded with a profile of what other interests this viewer has and, if you are really brave, you could send a message.
But if you decide to go back to your original position, you are lost, back at the top of the queue...This can be frustrating.
It is like visiting someone's house, knocking on the door, you look back to see the street view, you turn around again to say 'hi' to the person you were about to meet, but you find yourself back at the very top of the road....