Comma before which?

Question

TIL: You need a comma before which and another one at the end of the nonrestrictive phrase; for example:

Jeff’s new car, which is less than a month old, already started leaking oil.

And I learned that we can omit "which is" or "which" in the following sentences.

• This dog which/that is following us is very big.

  This dog following us is very big.

• This dog, which has 4 legs, is mine.

  This dog having 4 legs is mine.

My question is: Do we need commas for the last sentence?

Since "having 4 legs" is a nonrestrictive phrase.

This dog, having 4 legs, is mine.

Answer 1

A couple of remarks:

1. "[noun] having 4 legs" is not actually a normal way of putting this. "[noun] with four legs" is more usual.

2. So-called "restrictive" relative clauses actually often don't function to restrict what is being referred to. It's a bit of a misnomer, so some linguists prefer to call them "integrated relative clauses". It's fine to use an integrated relative clause in this kind of context.