Basically, from now on, i think that all posts should be behind and LJ cut. And rather than reply in the community, anyone whose answering replies as a comment.
The set out would be something like this:
Subject: Chemistry; lesson 1
Attn: All in Chemistry (also you can mention specific names)
I think this will help with interaction. And also, no particular time frame really needs to be followed, and anyone will be able to join in.
Hope this makes sense o.o;;;