Learn French: C'est le rôle le plus remarquable qu'elle interprète pour nous. - It is the most remarkable role that she is performing for us.

The subjunctive is triggered by the superlative phrase le plus remarquable (the most remarkable). In French, when you make a subjective claim using a superlative (the best, the most, the least) followed by a relative clause starting with que or qui, the verb in that clause usually takes the subjunctive. It shows that this is a matter of opinion or perspective, rather than a hard, objective fact.

Interprète looks exactly like the normal present tense. Is it really in the subjunctive?

Yes! For regular -er verbs like interpréter, the present subjunctive endings for je, tu, il/elle, and ils/elles are completely identical to the present indicative (the normal present tense). You can only tell it is the subjunctive here because of the superlative trigger. If the verb were irregular, like faire, you would see a clear difference (qu'elle fasse).

Why are there two le's in le rôle le plus remarquable?

In French, when an adjective follows the noun in a superlative sentence, you must repeat the definite article (le, la, or les). The first le goes with the noun (le rôle), and the second le goes with the superlative (le plus remarquable). If the adjective were one of the short ones that go before the noun, you would only use one article, for example: le plus beau rôle.