Confused about same subjects

Question

In many lessons, we're told not to use the subjunctive when we have the same subject in both clauses.  Yet a few examples in this lesson don't follow this rule.  Could you please help us to understand when the rule applies and when it doesn't?  Thanks.

Answer

Hola Marcos,The lesson makes it clear that "como si" is always followed by the subjunctive. The way that I explain this is that if you reflect on the purpose of the subjunctive, one of the fundamentals for using it is to describe hypothetical information i.e. "supposed but not necessarily real or true." Hence "como si" = "as if." Not real / actual but as if it were real / actual. Wishes and recommendations fall into the same kind of category. Effectively this rule sits alongside the one about one or two subjects but is not restricted by it. I hope that helps. Saludos. John

Answer

Hola Marcos
Not all sentences with two clauses with different subjects have to have the subjunctive. There is no clear cut rule for this, therefore, the subjunctive needs to be studied by seeing different cases, contexts, types of verbs etc to realize how the subjunctive/indicative works in each case. i think John's explanation about "como si" is very accurate because it does convey an element of uncertainty, and that would generally trigger the subjunctive. In "como si" clauses, using the same subject or different ones does not affect the mood used, so you can for example say: 
Ella continuó como si no ellos no estuvieran allí." (different subjects)
Yo me comporté como si (yo) fuera su superior." (same subject, still subjunctive)
Saludos
Inma