Fast formulas and use of brackets

Summary:

When writing if-then statements in fast formulas, is there any reason to use brackets for the condition?

Content (please ensure you mask any confidential information):

Looking at Oracle seeded fast formula code, there isn't really a consistent style used for brackets on if-then statements, even within the same formula. Examples:

IF prorate_start WAS DEFAULTED THEN
        prorate_start = l_card_comp_entry_start_date

IF (Additional_Pension_Type = 'CSSECS') THEN
(…
)

IF ENTRY_LEVEL = 'PA' then (
…)

Is there a rule, or is it just personal choice? I guess if you have a multi-line code block then you need to use Then (…), but other than that I don't see any restrictions. Having used other programming languages, the lack of a style guide feels quite noticeable.