I find this sort of ternary syntax to not be very readable. I think it should be easy to see conditionals when scanning through code at-a-glance.

In my opinion, clean ternary syntax should be short and sweet:

const something = cond ? 'val1' : 'val2';

const somethingLonger = isSomethingBiggerThanTen > 10
  ? someValueWhenItsBiggerThanTen
  : someOtherValueWhenItsLessThanOrEqualToTen;

As soon as the conditions are spanning multiple lines, it's hard to tell that there is a condition there at all. See my suggested edit

This condition was introduced in a commit 020bdd0d8d870a2a19c949c270036bd6679a27fb from 2017 which describes the purpose:

It should be impossible to make an anonymous user the admin of a thread

So we need to keep this condition. It might be a good idea to either, create a function with descriptive name e.g. canBeMadeAnAdmin or to add a comment describing why this condition is needed.