Prerequisite:

• Comments are enabled in moodle on system level.
• There is a course on http://MYMOODLEDOMAIN/course/view.php?id=COURSEID with comments block added
• Some comments have been added in the comments block

In the comments block, there are links to each commenting user's profile of this type:
http://MYMOODLEDOMAIN/user/view.php?id=USERID&course=COURSEID

But: "&" should be "&".

Now, if a user clicks this link, the course parameter isn't recognized and the user is forwarded to
http://MYMOODLEDOMAIN/user/profile.php?id=USERID
which he may or may not be able to view.

Replacing in /comment/lib.php, line 598
$c->profileurl = $url->out();
with
$c->profileurl = $url->out(false);
solves the problem, the user is shown view.php as desired, but I don't know which side-effects this has.