Or maybe two questions, depending on how y'all count these things.

There are two main forms of the explicitly plural second person pronoun in use on this board: you-all and y'all. Each of them has, in its respective possessive case, what I would think might be a grammatical error. In the former we have your-all's and in the latter, y'all's. First, they both violate the rule that possessives of personal pronouns don't use the apostrophe and, second, your-all's is redundant in that the possessive is shown both in the your and in the all's.

Any comments from our prescriptivist contingent?