Will the repentance of a person who uploaded pornographic stories to the internet be accepted, and who is unable to delete them after his repentance, and will he bear the sin of everyone affected by them?

If a servant repents to Allah Almighty with sincere repentance, it obliterates what came before it, and the lingering effect of the sin does not harm him if he is unable to erase it. The one who acts upon it is sinful, not the one who repents from it. Thus, the repentance is valid because the servant has done all that he is able to do, and for that which he is unable, he is excused.