This forum for communication removes the visual barriers that hinder some students from expressing themselves. (Para.3)
Meaning: As a place for communication, the online method doesn't require people to see each other personally. So some students won't feel it difficult to express their ideas.
visual: a. gained by or connected with seeing
Visual knowledge of a place of battle helps a general to plan his attack. 亲临战场对将军制定攻击计划很有帮助。
The visual arts are painting and dancing, etc. as opposed to music and literature. 视觉艺术是绘画，舞蹈等，与音乐和文学相对。
barrier: n. something placed in the way in order to prevent or control the movement of people or things
The police put up barriers to control the crowd. 警察搭起路障对人群加以控制。
The color of one's skin shouldn't be a barrier to success. 肤色不应该成为成功的障碍。
hinder: vt. prevent sb. from doing sth.; prevent sth. from happening
I'm sorry that some business hindered my answering your letter. 很抱歉，由于忙于一些事务，未能回信。
Don't talk to me now; you will hinder me. 现在不要和我讲，那样会妨碍我的。