I think moderation policy does play a role in the diminished participation of creationists.
The problem, as I see it, is that the requirement for scientific evidence based discussion greatly disadvantages creationists and ID proponents. What's really required to participate in a debate here is adequate knowledge of both evolution and whatever creationist or ID proponent viewpoint is under discussion.
There are actual scientists posting here, but there seem to be very few (probably zero) participants on either side who know ID or creationism any better than any lay person.
It's just far more difficult to find a minimally equipped ID proponent that it is to find an adequately equipped ID opponent. I won't deny that some anti-ID/creationist posters employ dog-piling, bad logic, and straw man attacks. But creationists don't seem to do much better in Great Debates where they get to agree on a single opponent. Creationists don't seem to do any better in threads where they propose the agenda.
My impression is that the typical ID proponent posting here knows very little about ID at all, and even less about evolution, cosmology, the scientific method, or any other relevant scientific topic. I'm not sure there is even a single exception. Often discussions don't go very far before before the ID proponent says something so fundamentally wrong, that even the non-scientists can see the error. When the ID proponent starts a topic, usually a blatant error is in the original post. Then the dog-piling starts.
Edited by NoNukes, : No reason given.