[troydavis]

Profile creation date is in the profile metadata. View source on https://substack.com/@michaeldehaan and find for: profile_set_up_at

The Instagram link is not the real author, it's just some random person with the same name.

I'd rather not share more about this person's pattern, but I've sent it to Dan and Substack. If you look closely at the links I pasted in https://news.ycombinator.com/item?id=40164077 (and profiles), you'll spot most of it. I'm sure they'll get better next time, though.

This is all but impossible to detect unless there's some pattern/tell. That's why I say to be somewhat skeptical of Substack URLs for now, unless you know the person giving it to you (or are otherwise sure the blog wasn't deleted). The real solution is for Substack to not allow people to re-publish on URLs already used by other accounts, so you and I don't need to try to figure this out on a case-by-case basis - in general, that's not possible.