The course/site description block inhabits the side block areas just like other blocks, but it is given a 10px border-radius in the standard theme (other blocks have no border-radius). On sites where this block is used I am often asked to override the 10px border-radius to make this block look like the others. Generally speaking, a site will look more professional if border-radius is consistent across all elements of a given type (in this case, blocks).

I realize that this block is special, and the developers want to accentuate it, but it seems like we would be able to leave it to theme developers to decide how they want to accentuate it, and otherwise leave border-radius the same as other blocks. (There is another aspect of this block's appearance that makes it special: this block has no header. So it still looks distinct without the special border-radius.)