comma with 'by no means': are, by no means, infallible

[angel heart1]

Hi,

Could you please explain why there is no comma surrounding by no means?


"these technological marvels are by no means infallible."

Taken from: http://grammar.ccc.commnet.edu/grammar/marks/hyphen.htm

Thanks.

 

[e2efour]

Why do you want to put commas there? Do you have a book which says that they are necessary?

 

[angel heart1]

What about "Use commas to set off expressions that interrupt the flow of the sentence," does it apply to this sentence?

Thanks.

 

[e2efour]

I don't remember seeing in print commas setting off by no means. This would be fairly unusual.
If you read the sentence aloud, it doesn't sound natural to pause when saying this phrase. By no means could be replaced by certainly not, and commas would not be used for this.