I ran into some adjectives that end in e for both masculine singular and feminine singular. For example:
anonyme, énorme, mince, chauve, informe
Can I safely assume that if an adjective ends in e for masculine singular, it will not take another e for feminine singular—except in the case of participles used like an adjective (e.g. informé but informée)? If my assumption is wrong and there are adjectives that take an extra e for feminine singular (thus ending in -ee), please give me some examples.
Are there any tell-tale signs of an adjective that was going to have an e at the end for masculine singular?
For question 2, please imagine a beginning student in French who, on seeing une boîte noire, thinks to himself, "Ah, for masculine singular I will remove the e. For example, un stylo noir." This stratagem works for him until he runs into something like anonyme.