Putting a monetary value on an activity that otherwise doesn't have it fundamentally alters how people think about that activity whether they want to or not. The best example is selling items in MMOs versus achieving them in game. If you put a $100 price tag on a weapon that otherwise takes 200 hours to grind it will ruin the satisfaction people that ground for it got from the item.

This happens... subconsciously and, I think, unavoidably. Commodifying core human interactions will affect sellers whether they want to or not.

We already commodify human interactions. Dating for starters (and arranged marriages before that). You could run the gamut of dates on your own or pay a matchmaker to set you up with a guaranteed relationship (or your money back). There's rarely a point to doing something the hard way if a successful shortcut is available, so long as all involved understand what they're getting out of it.

We're discussing "posting nudes like people post FB posts". What about that made it sound like commercial activity to you?