If you invoke the NetBeans IDE with the following additional startup argument (or add to your etc/netbeans.conf file) then pressing enter/return in a Ruby comment will continue the comment on the next line (e.g. indent as appropriate, then insert # } to continue the comment. Pressing backspace at this point will delete both the space and the # such that you can quickly finish the comment.
-J-Druby.cont.comment=true
This will probably be visible in options soon.