When the user moves over the "Email options" link, the cursor is the I-beam cursor; it should be the pointer cursor. So I added a line to the plugin's CSS so that the cursor becomes the pointer:
File:
buddypress-group-email-subscription/css/bp-activity-subscription-css.css
Add this line at the end of the file:
a.group-subscription-options-link { cursor: pointer }
http://wordpress.org/extend/plugins/buddypress-group-email-subscription/