Rp and erp is the same thing so not sure why you are saying one is ok the other is not, kinda weird from everything people told me what RP is. Aka acting and playing a char. Sexual stuff is part of this world lore, and normal living creature stuff. So it falls under RP.
Unless you will are saying that you rp without any flirting or sexual knowledge. Or even see it exist in the world. That would be bad RP would it not?
So if you are talking about just mod. So here is a question, what does these mods do that hurt the gameplay? You can't see it. Only they can. So why is it a problem if it gives no edge?