This is, fine.
You can never have a perfect system when it comes to banning, or removing people from an online community. Someone, somewhere, is always going to have their two-cents and complain about it because it affects them.
Overall, its good that there is no longer permanent bans for multiple offenses. There were some who got caught up in it, even with slight mistakes. So them being able to come back and enjoy the game is a good thing.
Also, this allowance, may actually have some of those who try to avoid their ban, not avoid it, now knowing that they are going to be able to come back after 90 days rather then suffer permanently being removed.
All this being said, I don't think it will make too major of a difference. There were trolls before, and there will still be trolls after regardless of this change. This at least opens up to people who do make the honest multiple mistakes, either through lag or whatever.