Sourcing art: Linking to the original art/artist in the post. This is something I assume most decent human beings will do, but a lot of people fail to do it anyway.

Getting permission: getting permission from the artist to post the work. This is something I hope most decent human beings will eventually do.

These are separate things.

"they do not allow repost without permission and people still do it anyway but"

There is no 'but'. This statement is like saying that someone let you petsit a dog and you stole it instead but is it okay because you paid for a name tag and collar for the dog. Just. No.

The situation continues to baffle me. Let us set aside artists who don't specifically state not to reprint art. People want their profiles to be happy and welcoming, but because of reprinters, they must put things like "don't reprint my art without permission." Not only is that already a rule in pixiv, but the artist says specifically not to do it. The direct refusal to heed this request is, in effect, insulting the artist. "Never mind the site rules, I won't even respect your wishes." Spitting in the artist's face. Even when they took the trouble to ask something that should be taken for granted.

When you ask someone to petsit a dog, you assume it won't be stolen, right? And if you specifically tell the person "I hope I can have my dog back when I return," that makes it all the more terrible for that person to have stolen your dog, right?

A new, shiny, name tag does absolutely nothing to absolve the thief, naturally.