The examiner can disagree with you, but they should never misunderstand you.
There are always several possible ways to say the same thing, and the first version you write might not be the clearest.
If you are thinking about what to say while you write, often you will cram several ideas into one sentence, separated by commas.
This can result in very long sentences and make your writing ambiguous, even if the sentence is technically correct.
So it’s vital to read and edit while you write, to be absolutely sure that you’ve expressed yourself clearly.
Count the commas
Count the commas. If there are more than two or three in a sentence, then unless they are carefully and precisely placed, you can end up confusing the reader.
So consider rewriting long sentences, splitting them into shorter sentences with fewer clauses.
There’s no absolute limit on the number of commas you can use, but shorter sentences are easier to read. Use longer ones if you need to, but only when necessary to clarify your point.