CSU1's English is pretty poor anyway, so how he can make judgements on 'foreigners' use of commas is beyond me.
I'm sure lots of other languages have their own rules on punctuation, just as they do for different word combinations and phrases, but we are all writing in English on this forum, and therefore it makes sense that the English 'rules' are applied.
The vast majority of non-English speakers on this forum have an almost impeccible record for using the language in the correct way - it's people like CSU1, and a LOT of Americans that ruin English.
The comma controls the pace and (if you like) the beat of the sentence. Where you want a brief pause, either to split up a sentence, to make a list, or just to provide somewhere to breathe.
The following sentence could be considered correct but it would be a lot nicer with commas at least to some extent as I will prove in the following sentence.
The previous sentence could be considered correct, but it would be a lot nicer with commas, at least to some extent, as I have tried to prove in this sentence.
The effect is subtle, but shouldn't be ignored. Too many commas can split up a sentence, and fragment it beyond it's originally intended meaning. Too few commas make it hard to read and understand. The balance is when a sentence has it's proper meaning relatively obvious, but is also not too much work to read.
Long live the comma (and the apostrophie, and the semi-colon, but I'd wager CSU1, and the aforementioned Americans (and lots of British people too) don't have much of a clue about them either).