I have no idea what courses I am going to moderate on if any. There was no discussion of the kind.
However, I can say that if participants know that they are assessed, they take part more actively. And it doesn't really matter what nationality they are. From the EVO courses that I take I can see that there are teachers who do the courses because they want to learn and there are the ones who, as soon as they find out that there is no certificate at the end of the course, withdraw. So you may start a course with 150 participants and finish it off with just 10-15 at most.
For a certificate to be issued some kind of assessment is needed (if it is not just a certificate of attendance/participation).
I think that assessment is important for a CP to work on the course but what is actually assessed may vary from course to course. And apart from this the person would actually like to know how s/he has done on the course. Isn't it the same in f2f classes? We do not assess all our learners similarly, do we? If a person is doing a course in academic writing, we don't assess the learner's speaking skills. But if a person is doing a course in General or Business English then we also assess the person's speaking.
I think the same is true for online classes. A participant doing a course in Learning Technologies should be assessed on how s/he can use and incorporate Web 2.0 tools in his/her lessons or what the person can actually do with the tools. Whereas for a person taking the TKT course would be more important to focus on general teaching skills, such as how to teach grammar, vocabulary, etc. and also on how to write a lesson plan.
Overall, I think that assessment is important but different skills should be assessed on each course.