According to this article the password 12345 was the third most popular password in use in the year of 2014. So why does SE use such a weak and commonly used password as a placeholder hint?
According to W3:
placeholder - represents a short hint (a word or short phrase) intended to aid the user with data entry. A hint could be a sample value or a brief description of the expected format.
I think this 12345 password hint could make some users assume that it's no big deal to use a weak password when creating a Stack Exchange account.
So could it be changed to something that resembles something not so weak like 6-8/Hrs||wks||mos||yrS or %UnIcOrN42%? Or maybe even just a short description instead like Create a Strong Password :).
Also, the example placeholder text goes against SE's own requirements/advice in the tooltip of must have upper case, lower case, and numbers or symbols in password with at least 8 unique characters.
So this situation is like lecturing someone to eat healthy food while, at the same time, you place a tray in front of them which holds a double cheezburger, chocolate shake, soda, and french fries.