On the Participants page, the 'With selected users...' dropdown menu options don't need any extra explanation. Also, they can include manual and (if enabled) self enrolment options, which are not mentioned in the help popup.

Thus I suggest that the help popup is removed.

Also, thanks to lucaboesch for pointing out that 'Add a common note', as mentioned in the help popup, is no longer an option. I have removed it in en_fix.