(I agree with everything you say but wanted to comment on a tiny three word snippet of your comment :) )

Nagging works if the person you're nagging has forgotten about you and if they hold you in high enough priority in the first place.

However, if you mail someone competent and organized, and they deliberately shelve you because you are not as important to them as other things they're doing, they'll get annoyed if you nag.

Like spam, nagging is an unpleasant intrusion on your attention. Automated nagging can't possibly improve upon that. Response expectation mismatch is a human problem with social solutions, not technical ones. If someone doesn't respond to me, I might know why, and if I don't I can restate my expectations in a manner appropriate to the relationship. Similarly, if someone requests something of me and has an expectation that I'll do it within 3 days, I can mail them to confirm receipt of the request and let them know it'll be more like 5. Expectation management in interpersonal relationships should be handled by the people involved.

You don't reply to an email and you get a reply a few days later: "Hey, I just wanted to make sure that you saw this. If you need any more details, just let me know. Thanks again!"

If you did mean to reply to that first email, this gets the job done. You can also customize the message to whatever you want. Even: "bump!"

It's a new name for spam. Renaming things has limited potential to change how we think about them.