I think restrictions can be fun if done well. The real thing that bothers me is, for instance, that MHaye’s claim was just God awful, poorly explained, and poorly timed, but people believed him because his role PM looked good. What I’d fear is that someone can play awful, their actions can result in bad stuff for town, and when confronted, they can post an honest PM and potentially avoid a lynch that way rather than argue their way out of it. For me, it goes back to the town being lazy except, instead of depending on a power role to save them they’re depending on an a player’s inability to duplicate the moderator’s style; it’s meta-gaming.
Of course, I think that restrictions (other than perhaps fun interesting role-related ones ala the Ventriloquist in Batman) of not being able to post role PMs can potentially limit gameplay. For the game that I’ve been making up in the back of my head, I’ve come up with other ways to mitigate it, and I think it will probably make it more interesting. So, for instance, if I want to prevent a specific person from posting their PM, I might include some information that appears innocuous but is valuable to someone else in a way that hurts them.
Of course, I don’t really want to give away the ideas I’ve come up with for my potential future game (since it would be closed), but an example might be how NAF was a dog in this game, and a particular scum may, knowing that he’s a dog, be afforded a tool to avoid being found out (like a dog treat, or whatever) such that, without posting the role PM, that person is able to be investigated, but after that part of the claim is revealed, he’d be immune; but since the dog aspect seems innocuous, no one could really be sure which parts of role PMs would and would not be safe. Another example might be that there’s an otherwise normal person, but he has a vendetta against someone and, upon learning his name, he attacks or blocks him or something. So, it wouldn’t be a restriction, per se, but it would certainly affect risk factor.
Now, if you’re scared, for the game I’m planning, I don’t think I’d do anything mean like that just to keep claims down, but I had become aware that some game mechanics could be abused in ways that they shouldn’t be and/or go against the flavor of a role. Then again, all of my ideas are still in the “oh, it would be neat to use a role like that combined with a role like that”, so who knows.