Usage of "oneself" (Sergei Polonsky, himself a one-time billionaire)

[sunsunmoon]

Sergei Polonsky, himself a one-time billionaire who lost part of his fortune during the economic crisis, goaded Lebedev on the pre-recorded show, announcing that he would rather punch someone than discuss financial issues with oligarchs.

(From Russian tycoon Lebedev punches talk show guest - Seven News Queensland)

Would the "himself" be necessary? If both "Sergei Polonsky, himself a one-time billionaire" and "Sergei Polonsky, a one-time billionaire" are correct, could you please explain the difference?

[Bennevis]

If you don't use "himself", it won't be a big deal, but the word makes it easier for the reader to get the irony of it all.

[Raymott]

Sergei Polonsky, himself a one-time billionaire who lost part of his fortune during the economic crisis, goaded Lebedev on the pre-recorded show, announcing that he would rather punch someone than discuss financial issues with oligarchs.

(From Russian tycoon Lebedev punches talk show guest - Seven News Queensland)

Would the "himself" be necessary? If both "Sergei Polonsky, himself a one-time billionaire" and "Sergei Polonsky, a one-time billionaire" are correct, could you please explain the difference?

Yes, it's necessary.
If you say A is a billionaire, and you haven't mentioned B, it would be strange to say, "B, a billionaire, punched A". You need something like "B, also a billionaire ..." or "B, himself a billionaire ..."

A billionaire is a person who's worth a billion dollars (or rubles or whatever).
A one-time billionaire is a person who used to be worth a billion dollars, but is no longer.

[sunsunmoon]

Since Polonsky used to be a billionaire and Lebedev is now a billionaire, is the "himself" necessary?

[Raymott]

Since Polonsky used to be a billionaire and Lebedev is now a billionaire, is the "himself" necessary?

Yes, it would sound odd without it in this context.

[sunsunmoon]

The other officer, a lieutenant, was charged with drunken driving and pleaded no contest, but got the charge dismissed on appeal.
(From ABQjournal.com: Albuquerque Journal login page)

Is The other officer, a lieutenant correct? Would it be incorrect to say The other officer, himself a lieutenant?

It seems that I still don't understand anything.

[Bennevis]

If you wanted to emphasize that it was done by someone whose job it is to protect the law, you could use "himself" here.

[Raymott]

The other officer, a lieutenant, was charged with drunken driving and pleaded no contest, but got the charge dismissed on appeal.
(From ABQjournal.com: Albuquerque Journal login page)

Is The other officer, a lieutenant correct? Would it be incorrect to say The other officer, himself a lieutenant?

It seems that I still don't understand anything.

Your link doesn't work.
There's no need to use "himself" here. Why would you?
I'll try to explain it again.

Item 1.
"Polonsky, a billionaire, became violent during a TV interview. He ended up punching Lebedev, a billionaire."
This is confusing. If this were longer, you would wonder who the billionaire was, and you'd need to go back over the text. However, if you say, "Lebedev, also a billionaire" or "Lebedev, himself a billionaire", it is immediately apparent that both are billionaires and there is no confusion.

Item 2.
"Polonsky, a billionaire himself, became violent during a TV interview. He ended up punching another guest."
The use of "himself" is wrong here. You only need to use this if you've already mentioned that someone is a billionaire.

Item 3.
As Bennevis has implied, you might use it in the following context:
"John Smith was arrested for drug trafficking yesterday. Smith, himself a detective in the Drug Squad, will face court next month."
Again, what "himself" does here, (especially if it appeared in a longer paragraph) is prevent the reader from momentarily wondering whether Smith was the arresting officer or the crook, and so it prevents the reader from having to read over the article again to clarify what's happening.

[sunsunmoon]

Thank you very much, Raymott. Do you and Bennevis agree with each other? It seems to me that you two have said something different.

[Bennevis]

Thank you very much, Raymott. Do you and Bennevis agree with each other?

I guess it's a rhetorical question now.