If you always defer potential conflict to seem humble
It sounds like you're saying a person can't be assertive and confident if they're humble. I don't really think that's the case.
I didn't want to give my perspective on the question I asked, because I want to see how other people interpret the question and the answers they give without my influencing them. But between you and me (and obviously anyone else reading this), I think if I were to give an answer to my own question the what defines distinguishes one type of person from the other is whether or not they're self centered and whether or not they exercise complimentary virtues such as compassion and wisdom.
If a person is dignified and compassionate, their compassion helps them to interact with others without looking down on them or otherwise mistreating them. If a person is confident and wise, they're able to recognize and compensate for their own short comings as well realize they don't always have the ability to handle every situation that comes their way.
I don't think any of these four attributes, dignity, confidence, compassion, and wisdom, when exercised, means a person can't be assertive nor does it prevent them from helping those in need or trying to rectify the injustices of the world. They may behave differently than you would expect someone to behave in certain situations, but that doesn't necessarily mean they're capitulating at the first sign of resistance or hardship.