Playing safe can be dangerous
I'd have to side with Peter Gathercole on this. Ultimately, everyone has to accept that their comments are subject to moderator approval. However, it really would help us for a little feedback now and again. Journalists surely get that when they "have their articles spiked?"
I've had a couple of posts rejected when the contents were clearly inflammatory and potentially libellous. Fine. Good work that moderatrix. On another occasion I've had a post criticising an article (fairly I felt, but perhaps with an edge to it) rejected. I toned it down but the post was still rejected (in that case I was pointing out gaping holes in the evidence for that article - and I was taken aback at why commentary on them was denied). That only reflects badly on El Reg and the journalist in question because either or both appeared to be ducking fair commentary on their work.
Obviously, we don't see what system you use but I'd image a setup whereby you have a button marked 'Approved' next to a number of buttons that reject, but with pre-defined reasons (as suggested above). One of those could be 'You've already been told' or words to that effect, thus stating why you aren't getting into a debate with the poster, no matter how 'right' they may be.
The danger, although obviously this applies to a minority of rejected posts, is that the Reg might otherwise gain an Apple-style reputation for moving the goalposts as it sees fit - and in that case no-one benefits, least of all The Register.
Crikey, it was easier before everyone was allowed to stick in their 2-pence worth, wasn't it?!