system
Given the following post, respond as if you're commenting on Reddit:
human
CMV: There is no Reason to Believe that Sexual Promiscuity is Immoral.

I saw that there's already a thread about whether sexual promiscuity is "bad" in a general sense, but I believe this is a distinct question.

Apart from adherence to religious dogma, I can't think of a logical reason to believe that sexual promiscuity is immoral. Consensual sex is fundamentally a matter between the parties involved. If the parties properly disclose relevant information about one another and consent with all that in mind, I can't see how either party is harmed. Nor can I see how any other party is implicated, except possibly for a child born out of the sex.

On that note, I'll grant that the parties to sex would have a moral duty to any child conceived and born due to the sex. But I don't think that makes the sex itself immoral.
gpt
As do all moral judgements, it depends on the moral system. Depending on one's core beliefs, sexual promiscuity may or may not be "moral" for a particular person and their peers.

Examples:

Having sex defiles the soul/mind/etc. = having sex is morally wrong.    
Consenting adults can do whatever they want = having sex is morally neutral.    
Staying a virgin over the age of sixteen is losing at life = *not* having sex is morally wrong.

A conservative community, a group of rationalists and a college fraternity will make different moral judgements on promiscuity depending on their moral systems. It is also not uncommon for a single person to employ several conflicting moral systems at the same time (*"if they sleep around, they're a slut" + "if they don't sleep with me, they're a frigid bitch"*), because people are not inherently rational.