There's up to four icons in the last column of the manage enrolments page (http://your_moodle.net/enrol/instances.php?id=101).

Two of them are iconsmall and two of them are smallicons which have different styles applied that makes them look untidy.

In particular this line from base/style/core.css:

.action-icon img.smallicon

The up and down arrows beside them would also line up better if the spacer image was given a width.