A learner is an inquirer. This person asks questions. They want to know, and are not afraid to reveal what they don't know. As Bob Edwards said in a comment, one of the qualities he thinks of in a learner is humility. I think humility enters in here. Inquirers do not sit back and pretend to know it all. They recognize what they don't know and will ask. Learners of Jesus have more to learn than we ever can in a lifetime, so we must be always inquiring.
A learner is also a communicator. As learners of Jesus, we are to be communicators. It's easy to get the idea that we are to simply communicate the "gospel." While we are to let others know that there is a King and that God is making all things new, we also need to remind our brothers and sisters in Christ of what the love that the Father has shown to us. We also need to remind each other that we are in this together, communicate our love for each other, and encourage each other to love and good deeds. Communication is something we all need to work on. How many problems would be solved if we really sought to communicate with each other instead of just talking at each other.
Another learner quality is reflective. This is the quality of taking the time to think things over. Many followers of Jesus would call this contemplative. While it is true that some are called to a lifestyle of contemplation, all of us could benefit by taking some time out of our far too busy lives to just be in Abba's presence, thinking about what he has done for us and listening to his voice. Jesus said that his sheep would hear his voice. That is tough to do with so much noise around us, but it is a quality that is vital to our spiritual life.
On top of the qualities of caring, principled, thinker, open minded, and knowledgeable, let us also be inquirers who communicate, and who also take the time to reflect.