Themes

It's a nice idea and I'm not saying it's not needed but the button doesn't do that.

What the button does is take you back to the course homepage but you may not have come from the course homepage. For examples you may have come from an activities overview page, if that makes sense.

In other words, you may have got to this forum from http://moodle.org/mod/forum/index.php?id=5 and having a back icon for that button would be misleading as it wouldn't take you back to where you came from - it would take you to the course homepage.