From the other side of the desk, wouldn't you be impressed if you had a candidate come in for another interview, and they explicitly tell you that you had interviewed them previously and they understood their weaknesses at that time. And they're looking forward to show you just how much their chops have improved in the meantime, and then proceed to do just that?
If I'm very proud of my company, I might be flattered that they too want to work at the same company so much. If my company's just a'ight, I'll think "why? and where have you been working in the meantime?" Additionally I might feel a little sorry for them, at first. If they actually do amaze me with how much they've improved, I would kick myself for failing to notice their potential the first time, and recommend them for immediate hire. I don't think I'd ever feel impressed with them. They'd deserve to feel impressed with themselves though, unless they totally blow it / show no improvement in which case I'm back to just feeling sad for them...
How can I understand my weaknesses at the last interview if you didn't tell me what they are in the first place? Surely you don't expect me to improve upon a total lack of feedback?
I used to worry about blanket rejections. Not any more. They're not actionable, so I ignore them.
From the other side of the desk, wouldn't you be impressed if you had a candidate come in for another interview, and they explicitly tell you that you had interviewed them previously and they understood their weaknesses at that time. And they're looking forward to show you just how much their chops have improved in the meantime, and then proceed to do just that?