an aspect of the article which we think is positive.
Which noun phrase are we thinking is positive? Is article positive, or is an aspect of the article positive ? Thank you in advance.
The relative clause which we think is positive can modify either the noun phrase the article or the noun phrase an aspect of the article.
If you are talking about one article, then in all likelihood, the clause modifies an aspect of the article.
If there are two or more articles under discussion, then it could very well modify the article, so that "an aspect of [the article which we think is positive]" is the correct way to parse the phrase. This would be in opposition to, for example, "an aspect of [the article which we think is negative]".
Part of this is going to be dependent on the topic under discussion. Sentences and other clauses are usually discourse dependent regarding their interpretation. Often we can't determine the meaning of a sentence, clause or phrase just by looking at it alone.