As to the point of identification questions specifically, I'm afraid the community has decided to no longer support them on this site, so your question likely won't be appropriate to begin with. However, regarding your general question about describing a very sexual scene:
First of all, textual descriptions are much less problematic than pictorial ones to begin with. So the question of NSFW should already be out of the way, if that even is a problem to begin with. If you're worried about your boss not just seeing the images on your screen but actually reading the tiny little letters on it, maybe you shouldn't browse movie sites at work. ;-)
As to the matter of sexuality and sexual descriptions in general, the emphasis is that it shouldn't be tasteless or overly indulgent. But from both the way you describe the scene and the way you came to meta first in order to gather feedback, I would assume that your description of the scene will likely be totally fine.
We are legally a 13+ site here, but that doesn't mean anything sexual is off-topic. Afterall, we're discussing films here that (together with the questions about them) exhibit way more serious and problematic themes than a "subtle" sex scene and prohibiting any kind of discussion of sexuality here would hinder many serious film discussions. Just remember to keep things "tasteful and professional". So no, there's no explicit and clear rule about it, other than neither being inconsiderate of the professionality of the site nor being overly protective of the sensitive ears of little 8-year old Timmy, since neither is he allowed to register on this site, nor is it our responsibility to protect him from the internet. Your meta question suggests that you're mature enough to find a good balance, though.