Punctuation differs from publisher to publisher, but in all cases is used to separate and group instructions. Typically, commas, semi-colons, colons, and dashes are used to separate. Parentheses, brackets, curly braces, and asterisks are used to group. Commas and semi-colons are used to separate each part of an instruction making the parts a bit easier to see and read.
Instructions and parts of instructions are grouped for several reasons; 1) To indicate that multiple stitches are to be worked into the same location and, 2) To indicate that instructions are to be repeated.
Parentheses are most often used to group stitches to be worked into one location. For example, “(k1, p1, k1) in next st” indicates that all 3 stitches within the parentheses are to be worked into the next stitch before it is removed from the left needle. Brackets, curly braces, and asterisks paired with “repeat” are used most often to group instructions to be repeated.