If that were truly the case, Camikaze, you should get rid of the opportunity to privately PM appeals to moderators too, since that's just displacing the initial anger of the infraction from the thread to the location of the PM, cluttering up mods' inboxes and giving them additional work. Same logic applies, really.
I wasn't meaning to suggest that posters shouldn't be able to appeal at all because they might still be unhappy, just that a managed PDMA system would seem unlikely to make them much happier. So such a system isn't particularly attractive at least to the extent that that is one of its supposed benefits.
The idea of accountability is an interesting one, because you seem to be describing it in terms of government (with democracy therefore being a crucial element). Perhaps unfortunately, as Lefty alluded to earlier, moderator power derives from Thunderfall's ownership and complete control over the site (exercised through 'site administration'). It's necessarily the case, then, out of the sheer quasi-fiduciary nature of a moderator position, that staff are accountable to site administration, and site administration alone. Now, that statement can superficially seem quite a harsh one, and probably needs some qualification to explain it fully. It's
not saying that the staff should not care about the community, because site administration has prescribed that as the moderators' job. It would therefore be a misuse of our power, or an abuse of our position, to not act in the community's interest - but this is the community's interest
as defined by site administration, and a failure to act in accordance with that definition would equally be a misuse of our power, or an abuse of our position.
And this is not something that can be changed as a matter of policy; it's simply a description of the nature of forum ownership. If we say that the public can vote in moderators, this still proceeds from the fact of site administration's control, not from some inherent sovereignty of members which would form the basis of site governance. Similarly, site administration could give more of their power over moderators to some group of members (including all members as a whole), but accountability would still ultimately lie with the site administration.
Working public accountability into that system, then, involves moderators being seen to be accountable to the site administration (not actually making moderators accountable to the public, which is a democratic notion). This is currently achieved through the site administration either publicly supporting moderators, or in relation to an individual action, by privately supporting that action through the appeals process. It could also be achieved through site administration publicly admonishing moderators, but I don't believe that's what's being proposed.
I don't think it could be contended that the moderators are not accountable to the site administration - the statements of support from site administration of the moderators make it perfectly clear that moderators are acting in accordance with what site administration wants. What is being asked for, then, is
more control over site administration itself. That is, the issue is not moderator accountability, because it's clear that moderators are accountable to those who they are meant to be accountable to, unless it is contended that the site administration has lost control of moderators (by losing the password to the AdminCP, perhaps). The issue is rather who moderators are accountable
to, with the request being that the community should at least partially take the place of site administration. Or alternatively, this could be phrased as a submission being made to site administration to reconsider what the community's interests are.
That's a fairly theoretical take on the 'can we please have PDMA' request, but I think it's important to recognise that allowing for PDMA threads doesn't actually make moderators any more accountable to members; you state this in a different way by saying that moderators would still have an 'invincible suit of armour'. It just means that things are explained publicly, which would hopefully make people happier. But if it's not making people happier (and this is the point of my previous post), then there's not much point to it.
Which in the end means the key question is whether third parties would be made happier by the presence of PDMA threads, and whether that happiness is worthwhile in the sense of being the most efficient way to achieve happiness with the limited time moderators have. For example, more time spent responding to PDMA leads to less time dealing with reported posts - are third parties made happier by moderators spending time on PDMA, or by having a report responded to? If PDMA threads were to make moderators more reluctant to deal with particularly litigious individuals, would this make people happier than a system which allows those people to be more easily dealt with? etc.