Parenthesis: A useful (and delicious) form of punctuation

Does it matter whether you number lists like this:

1) Mix your dry ingredients together.

2) Add eggs. Beat well with a whisk.

3) Slowly add softened butter.

Or like this:

1.) Mix your dry ingredients together.

2.) Add eggs. Beat well with a whisk.

3.) Slowly add softened butter.

Or like this?

1. Mix your dry ingredients together.

2. Add eggs. Beat well with a whisk.

3. Slowly add softened butter.

Apparently so. Is this extraordinarily picky? Yes. However, apparently parentheses have one specific use: according to Webster's Dictionary, for adding "parenthetical" information.

Now, whether it is fair to eager grammar students to use the word one is defining within the definition for that word (i.e., using the word "parenthetical" to define "parentheses") is a conversation for another time. However, Casagrande essentially tells us that parentheses are only to be used for side comments (so numbering like 1.) or 1) is basically a no-go).

As for the matter of brackets ([ ]), Casagrande tells us that they are to be used as parentheses within parentheses -- or, in other words, as a side comment on a side comment. She notes that this practice is ridiculously confusing and impractical, but just think of all the fun you could have making your writing as cryptic as humanly possible!

• Parentheses are rounded brackets (also called lunulae [but this was back in the day] by some grammarians) and are used to include parenthetical information (otherwise known as an aside [which is often referred to as a side comment] by the author).

While Casagrande's rant about the uselessness of brackets is undeniably funny, she fails to address many of the incredibly useful ways that authors use brackets (as outlined by Truss), such as:

• Altering a quote with ambiguous pronouns so that it makes sense to the reader (changing "It caused a stir at the convention" to "[Casagrande's statement] caused quite a stir at the [grammar] convention").
• Indicating an original misspelling with the enclosed phrase sic (She asked for "a packet of Starbust [sic]").
• Enclosing ellipsis when words are left out of a quote ("Finally looking this up for the first time, I see that [...] the words 'ellipsis' and 'ellipses' are not interchangeable" [Casagrande 75]).

What is the (undeniably) useful lesson? When unsure about punctuation, check multiple (trustworthy) sources.