I find myself disagreeing with many of the examples. E.g. according to the article:
Bad: It is quite difficult to find untainted samples.
Better: It is difficult to find untainted samples.
Bad: We used various methods to isolate four samples.
Better: We isolated four samples.
Something being quite difficult reads significantly differently than just being difficult. You haven't made the sentence better, you've changed the meaning.
And the fact that you used various methods instead of a single method is information missing from the second sentence.
Bad: It is quite difficult to find untainted samples. Better: It is difficult to find untainted samples.
Bad: We used various methods to isolate four samples. Better: We isolated four samples.
Something being quite difficult reads significantly differently than just being difficult. You haven't made the sentence better, you've changed the meaning.
And the fact that you used various methods instead of a single method is information missing from the second sentence.