Please stop reporting all OF models as spam. If a post is off-topic, report is as off-topic. If community rules forbid OF models from posting, report that. If a user is flooding a sub with multiple posts a day in a row, that’s a legit report as well.
Otherwise a post by an OF model is not in and of itself spam, even if it is made by a <ferengi>female</ferengi> with the temerity to control her own sexuality.
They aren’t just advertising though, they are also contributing. A better analogy is food companies going to a food convention and giving out free food. The site would be a lot quieter without their contribution.
even with the food subs comparison the food companies would be “contributing” too, but with self-serving memes that are really just ads. See twitter for a solid example.