I have noticed before, not only on MDL, how some people derive a weird satisfaction from being the first to comment and/or review. In order to be the first, some are ready to write the most ridiculous things 10 minutes in, such as "wow, finally I'm the first!" - very helpful indeed! - or "I love this drama so much I'm addicted", ignoring the obvious, which is we are all here because we are addicted to some extent. The fact that X is addicted on episode 1 does not help me chose what to watch next.
This urgency to comment about things reflects in what Jeanie points out: they don't read the rules, and if they do, they don't care.
I agree however that dropped dramas are a different matter. If the reviewer explains his/her reasons for dropping the drama at some point (possibly not after 2 episodes but a little further in), I think it can be as helpful as any review of a completed drama. I suppose it all boils down to being able to motivate, whether one has liked a drama or not.