Steve, I have seen several instructors us the "acknowledgement approach" and have stuck with it because it works for them. The positive recognition of the student is very powerful for many - catching them doing something right! It is a good idea, when implemented with care. I would be careful in the assignment of 'extra points' to be sure you follow the institution's policies. Reinforcing ppositive behavior is good, but if it impacts the grade indicating a student's academic performance is more than it actually is there could be a problem. Also, many LMSs provide the option for 'pop up' of new announcements. Many online instructors leverage this option to get a higher read rate. Craetivity is a strong ally to any teacher. Check with instructors at your institution to see if there are other remedies implemented within that system.