Thank you for this post. I agree with you completely on the issue of spam, and actually what constitutes as spam.
I agree if 'update soon' was the sole thing written on 5 pages by the same person, yes that is going overboard. However if a reader writes 'update soon', it may just be their simple way of commenting.
Some readers are hesitant to comment on threads, because they feel they cannot confidently express themselves in words. By putting restrictions on what should be allowed to be written as a comment, we are limiting them from saying anything at all. It is not just about a simple 'congrats' or ' update soon'; it is about our choice of voice, which we should be allowed to use as we want as long as we aren't being obscene or hurting someone in the process of it.
I do hope that the DT's discuss this matter and come up with a viable solution in the near future.