Every time you perform an action like commenting, you expect it to maybe update a few things. The post will increase the number of comments so it updates that, your comment is added to the list so those links are created, your comment is written to the database itself, etc. Each action has a cost, let's say it costs a dollar every update. Then each comment would cost $3, $1 for each action.

What if instead of doing 3 things each time you posted a comment, it did 1300 things. And it did the same for everyone else posting a comment. Each comment now costs $1300. You would run out of cash pretty quickly unless you were a billionaire. Using computing power is like spending cash, and lemmy.world are not billionaires.