I think it is going to get worse - because not only is the attention span going down, but it creates a learning gap to increase it again.
Well funny you ask, because I typically copy and paste the quotes I respond to in the moment, before even finishing the article.
I thought I was the only sucker that did this! :D
I also find that this allows me to better connect to my stream of thought in the moment, so I don't lose what I was thinking about as I progress through your writing.
I reckon there is value in it and doing so leads to more considered answers. Many just answer to one particular point that they remember at the end, losing what they had gathered along the way.
There's benefits to both approaches. When you comment to a point in the moment, you don't get to see the big picture until you're done with the comment. But you're right, I prefer to write what I feel when I feel it so it stays fresh.