I really think "Community-Wiki" should be saved for the gospel, set-in-stone, this-is-how-you-do-it answers (like this work of art: How do I install the Nvidia drivers?). I really don't think it was meant for situations like this.
In your first linked example (I was just reading that question), I think that one should be closed as "too localized." There really isn't a solution to it, other than to say "Don't mess with your
.bashrc without really knowing what you are doing, because you may not be able to open a terminal session."
But your second linked example is definitely the more relevant one here. In an ideal world if a comment was (or led to) a solution, then that comment should be converted to an answer. And in a really ideal world, that answer should be "accepted."
However, the best we can really do is to post a comment notifying the user in-question to convert his comment to an answer. If that happens, then we hope that the OP comes back and "accepts" it.
EDIT- And here is an example of that happening (to me) this morning: Get all binded ip addresses