Courses may allow or deny access to guest (i.e., non-enrolled) users. In the "Available courses" list, this is indicated by the presence or absence of the "guest" icon. If guest access is allowed this icon is appended to the course title. The icon is also linked to to course home page, and its ALT attribute is, "This course allows guests to enter."
Why it matters
The primary problem is that the icon is also a link. This means that in one of the most common screen reader navigation patterns, reading through a list of all links on the page, the text, "This course allows guest access" appears once for every course. These links are useless in this context because the link text doesn't tell the user where the link leads.
The second problem is that an important course property (guest access not allowed) is indicated only by absence of this icon. If all courses are so configured no indication is provided.
The icon should not be a link. It might be very successful as plain text (e.g., "Open to guests" or "Guest access allowed"). If an icon is desirable and understandable to sighted users, the could be replaced by an icon using CSS.