So, I have a sentence,
You can show it to him, if you haven't done it already.
My reasoning for this comma is that I don't really put a condition per se before my interlocutor, I'm merely saying "I allow it", "I don't mind", and then I sort of add "well, I guess - if you haven't done it already", but you can do whatever, I don't mind.
Does it make sense? Is it just a stylistic choice? Or is it plain wrong, and we shouldn't use a comma before "if" as per the general rules with conditionals that we always follow?