There's a bit of broken (or missing) logic in ACharacter that doesn't account for users having released the jump button. This is a well known issue, and there's even video's describing how users can overcome it:
Despite this, it seems better to have this work as expected by default.
Expectation: After the character has jumped the first time, nothing happens.
Actual: The character can repeatedly jump (forever).
Head over to the existingAnswerHub thread and let us know what's up.