In addition to the excellent points made by steventhedev and koper:

user.password = await hashPassword(user.password);

Just this one line of code alone is wrong.

1. It's unclear, but quite likely that the type has changed here. Even in a duck typed language this is hard to manage and often leads to bugs.
2. Even without a type change, you shouldn't reuse an object member like this. Dramatically better to have password and hashed_password so that they never get mixed up. If you don't want the raw password available after this point, zero it out or delete it.
3. All of these style considerations apply 4x as strongly when it's a piece of code that's important to the security of your service, which obviously hashing passwords is.

Figuring out what the code is doing is not the hard part. Documenting the reason you want it to do that (domain knowledge) is the hard part.

Ew no.

Abusing language features like this (boolean expression short circuit) just makes it harder for other people to come and maintain your code.

The function does have opportunity for improvement by checking one thing at a time. This flattens the ifs and changes them into proper sentry clauses. It also opens the door to encapsulating their logic and refactoring this function into a proper validator that can return all the reasons a user is invalid.

Good code is not "elegant" code. It's code that is simple and unsurprising and can be easily understood by a hungover fresh graduate new hire.

Why the password.trim()? Silently removing parts of the password can lead to dangerous bugs and tells me the developer didn't peoperly consider how to sanitize input.

I remember once my password for a particular organization had a space at the end. I could log in to all LDAP-connected applications, except for one that would insist my password was wrong. A trim() or similar was likely the culprit.

A quick glance and this seemed nothing to do with self documenting code and everything to do with the flaws when code isn't strictly typed.