The biggest problem with this convention is that new & anonymous users cannot comment, so the only option they have is to edit the post. These then get rejected out of hand and useful contributions disappear. This is doubly wasteful since this behaviour often discourages people from every contributing again.
No, new and anonymous users do have another option, they can post their own answer.
That's irrelevant anyway, since that's not what happened here. The author of the post tried to edit his own answer with a second account. He should have just used his original account and this would have never happened.
No, new and anonymous users do have another option, they can post their own answer.
Which is less wrong than an edit but it`s still wrong when the appropriate response is a comment.
A community can be judged by it`s responses to newbies. By this measure it fails miserably since the most common feedback many newbies get from SO are bare downvotes and rejections. What should happen is a polite response explaining the problem and the what should be done to correct it.
Speaking as a contributor and reviewer on Super User and Stack Overflow, your opinion of what should happen is shared by more or less everyone who is an established member of the community. The trouble is that there are a lot of newbies, many of whom don't take time either to read the "about" and "how to ask good questions" advice which the sites make prominently available for new users, or to characterize their problem in sufficient detail to make it solvable, or to search for the trivially obvious answer to whatever question they're asking.
Once you've seen enough of this sort of thing -- and, again, especially on the highly popular sites there is a lot of it -- there's a certain fatigue which sets in; you get jaded, I suppose, and that seems from what I've seen to be the proximate cause for newbie questions getting downvoted to oblivion or flagged for closure without anyone taking a moment to advise the asker on what he should've done differently.
Is this ideal? Of course not; in fact, it's not even close, and I say that as someone who has considerable experience with the phenomenon so described. But Stack Exchange sites are moderated by volunteers, and you can't issue ukazes to volunteers without a significant risk of losing them -- after all, if you make them not want to do what they do, they'll just stop doing it.
In any case, just as a community can be judged by its attitude toward newbies, so can those newbies be judged by their attitude toward the community in which they attempt to participate. As in any other such case, it is entirely reasonable for those who have invested time and effort into Stack Exchange sites to expect that new users will deport themselves with respect for the rules and mores of the community.
With regard to giving the ability to comment to new and unregistered users, there's a problem similar to that of low-quality newbie questions; so to broaden the provision of commenting privilege would produce an instant and enduring deluge of spam. You really can't expect volunteers to handle sewage disposal, especially when the sewage is deep enough to require hip waders. Again, this is not ideal, but it is a consequence of the Stack Exchange model's basic assumptions, and I'd have to say that model has acquitted itself well enough in practice to vindicate the claims made on its behalf.
