Is a comma needed in a backwards sentence? (E.g. "For B do A")

It looks like the consensus in the comments is that there is no strict rule here.

It also looks like the actual rule is either to follow whatever guidelines one needs to follow, or, in the absence of such guidelines, follow whatever is clearer.

It also looks like the shorter the sentence, the less chance the comma will be needed, and the longer it is, like this sentence, the more likely.

I'm writing this answer not as an expert, so in case you think this is wrong, or that I misunderstood the aforementioned comments, please feel free to inform me in a comment, or write another answer.