Having sex with someone you don't trust to be courteous with your feelings and reputation is reckless. If you (the royal you, not anyone in particular) choose to do this then I suppose that being embarrassed by what someone is sharing is your own fault.
If you don't trust me enough to be courteous about the details of your life and minimize harm done to you by something I might say ... why did you have sex with me? That's just weird.
Originally Posted by Nudge
One thing to note is that disclosing sexual details means providing information about a third party who may not want to have the information shared.
I may be comfortable sharing sexual information about me and my spouse with my girlfriend, but what if the spouse wouldn't want the information shared. Consent of every party involved is important.
I don't ask people specifically what details they are comfortable with my sharing with other people unless there is some particular reason to do so (I've never encountered that reason, but I presume it could be out there). The reason to be concerned about what information should be shared is generally "Will this information be used to embarrass or injure me at some point in the future". I guess there are some people who are touchy about information being shared about themselves for reasons other this fear of potential harm... but I don't know what those reasons would be.
I make sure to get to know my partners and to understand if they are paranoid about being injured or embarrassed, or if they live their life in a more "open book" fashion. I also consider the person I am speaking to and whether or not they have a tendency to gossip or have a problem with their brain-mouth filter. Once I discover that someone has a brain-mouth filter issue I stop sharing with them (anything, really). Once I discover that my partner is paranoid about their details and doesn't trust me to be careful with them... my guess is that relationship is not going to be very intimate.
So I would say, consider the source of the information and who you are sharing it with should be the most important. Getting consent to tell someone about a sexual encounter with someone else isn't something I find practical.