Very interesting discussion, as always. Like most things in D&D, it's all in the presentation if you ask me.
As a DM, over the years I've narrated slavery, torture, genocide, temptation, flirtation, sex... just about everything, but it's never been a question of what is comfortable at the table because I don't feel the need to switch out of 'standard 5-speed stick' D&D.
Fights are narrated as amusing, over-the-top displays of heroism and/or stupidity and/or luck. Sexual encounters are narrated in exactly the same way. As a for instance, in a recent session the party arrived at a desert city only to be greeted by no less than the Khan himself, a perfect picture of strength and charisma. He was immediately set upon by the notorious flirt of the party (a high-Cha Sorcerer played by a guy, by the way), only to have her approaches reflected back at her ten-fold. Suffice is to say, they both got lucky that night, and DM and players had a good laugh. Nothing uncomfortable, no dice rolls required, everyone happy. Mature content? Yes by many definitions, but I would bet real money that the exact same bit of roleplaying has been executed a thousand times before at hundreds of different tables.
I guess my point is, D&D doesn't *need* its mature content codifying, and I don't *need* suggestions on handling these subjects tactfully. The D&D language I've been speaking for 25 years is perfectly adequate.