If I were a butterfly, I'd thank you Lord for giving me wings

OR

If I were a butterfly I'd thank you Lord for giving me wings

In that aspect, it does the job well

OR

In that aspect it does the job well

Yet despite expectations of a downgrade, during last week's financial market rout investors plowed into U.S. Treasuries.

OR

Yet, despite expectations of a downgrade, during last week's financial market rout investors plowed into U.S. Treasuries.

In Holland untill the age of 27, people are obligated to work or study

OR

In Holland untill the age of 27 people are obligated to work or study

OR

In Holland, untill the age of 27, people are obligated to work or study

In the past, I generally sent my resume in Word format because that was what was usually requested.

OR

In the past I generally sent my resume in Word format because that was what was usually requested.

Commander Christine Jones, from the Met, said ...

OR

Commander Christine Jones from the Met said

For ipv4 TCP there are various criteria for GRO matching.

OR

For ipv4 TCP, there are various criteria for GRO matching.

In a perfect world we wouldn't books like this

OR

In a perfect world, we wouldn't books like this

Thanks very much. I'm trying to get a grip over the comma :-)
Hello, rebooting - and welcome to English Forums. These are correct commas:

If I were a butterfly, I'd thank you, Lord, for giving me wings

In that aspect, it does the job well

Yet despite expectations of a downgrade, during last week's financial market rout, investors plowed into U.S. Treasuries.

In Holland, until the age of 27, people are obligated to work or study.

In the past, I generally sent my resume in Word format, because that was what was usually requested.

Commander Christine Jones from the Met said

For ipv4 TCP, there are various criteria for GRO matching.

In a perfect world, we wouldn't books like this
Thank you MM.

Yet despite expectations of a downgrade, during last week's financial market rout, investors plowed into U.S. Treasuries.

I thought there should be a comma after 'yet'. Why is a comma inappropriate there? Thank you very much.
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Simply too many commas. A couple of short adverbials, or a short conjunction and adverbial, etc, can omit the comma when it slows the flow overmuch and the text remains clear without it. A comma is needed much more after 'rout', where the sense is momentarily confused without it.
MM,

In Holland, until the age of 27, people are obligated to work or study.

Isn't that a restrictive clause? so why are we putting comma around it? Thanks a bunch
It is just prepositional phrase, not a clause, but anyway, the commas are necessary to make easy sense of the syntax: that is the primary function of commas. If the prepositional phrase were extraposed, there would be no need for one.
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