Here’s a Good Reason to Be Wary of Overly Polite People (nymag.com)

There's excessively polite people with a hidden agenda, and those without. I don't think the ratio is strong enough in favor of evil to warrant too much effort. If you think the evil density is higher, I suggest testing to find out, rather than just wondering. Borrow some money off them, or ask them to help you move, and see how it goes.

If they pass your test, you need only watch for the long con, and its much less common. Unless they change.

Unless they are autistic and genuine without guile.