Where, exactly, are the deficiencies in the PerlMonks FAQ? It seems to me that the FAQ is plenty clear on all of the issues you mention; but I admit that I may be too close to it to see it objectively.
I've /privmsg'ed several new Monks letting them know their Message Inboxexists after it became obvious they did not know about it. IIRC, our own very savvy ELISHEVA found /msg'ing a usergroup (as opposed to an individual user) neither intuitive nor obvious.
I have, somewhere on my rather long "To Do" list, a notation that it would probably be a good idea to place a "/msg usergroup" link on each usergroup page, like exists currently for plain ol' users. I'm not sure I have the pmdev chops to accomplish this by myself, however. I've certainly not had the time to delve into the idea just recently.
Perhaps I need to do more reading of the site docs with an eye to this specific issue, to try to see if some improvement can be made in my role as SiteDocClan.
Looks like planetscape covered finding one's Inbox better than even I could. But I would add that just using it can be confusing. For example, the "move" section (the bottom right area) and the checkboxes around "showing messages" are all a bit confusing. And Super Search is not only a bit confusing at first but also very intimidating. Another example are the confusing choices for Consideration. I actually brought that up when I could start considering nodes but experienced Monks didn't think it was all that confusing. And now that I have been voting on considerations for several years I don't find them confusing either.
I think the reality is that the longer we have been at The Monastery the more we take the learning curve for granted. Maybe that applies to Perl as well! :-)