Learn English – Comma in “for all”-sentences, after “In most cases”

The meaning is the same either way. However, when writing sentences - especially when writing something formal such as an essay - one should use commas after their transition word or phrase that starts a new sentence.

For example, notice how I started this sentence with my transition phrase "for example" and put a comma after it? Of course, commas are useful for starting sentences out, as well as breaking up the thoughts in a single sentence.

I italicized the transition words/phrases above. Here is a site with phrases if you want to know how to add variety to your words. It's divided into different categories.

I'm American and I can tell you that it's not dialectal. What you are really saying is "such that there were two chairs" with the parenthetical "for every person." So there are two correct ways to write it:

1. ...such that for every person there were two chairs.
2. ...such that, for every person, there were two chairs.

The former is more likely if it's a short sentence and the commas don't make the sentence difficult to decipher or ambiguous. (It may also be more common in America). The latter is more likely if the sentence is long or ambiguous without the commas. In speech you may well hear *"such that for every person, there were two chairs" but it is not correct to write it that way. You can choose to put a comma on both sides of a parenthetical or neither but you can't have one comma.