The sentence that punctuates a parenthetical expression correctly is:
The leaks in the bottom of the old pair of waders, moreover, meant that her feet were soaking wet as well as cold.
A parenthetical expression is an additional element or commentary that can be removed without altering the core meaning of the sentence. It is typically set off with commas, parentheses, or dashes. In this example, "moreover" is the parenthetical expression, and the commas are used to separate it from the rest of the sentence. The other sentences have incorrect or unclear usage of commas with their parenthetical expressions.