Yes, this is partly in response to a recently catacombed post. The mod team held views on both sides of the matter as to whether to moderate or not, and the ending decision was that not only would we act in this case, but that we also ought to expand Rule 6 to be a little more inclusive on what we defined 'inappropriate' to be.
Full disclosure on my part, regarding my opinion: I personally tend to take an "it's evolution in action" view towards this sort of thing. If something is spoiler-tagged with the warning that it is NSFW or potentially objectionable (how are asked to do it in OOC ingame, for example), the sensible policy, to me, is that curiosity killed the cat: Namely, if you click on the link after the warning and don't like what you see, it's your own goddamn fault for letting your curiosity get the better of you.
With that said, however, I also noted that spoiler tags on Backstage do not use "click to show/hide" functionality on regular desktop and laptop computers (as far as I know), but will on mobile devices with touchscreens like phones or iPads. As a result, people can sometimes see things without clicking on them, and thus I personally would prefer that people put links to such images inside spoiler tags rather than displaying the image itself inside the tags if for some reason they absolutely must do so.
As for including sexytimes or violence in your writing... I think the prevailing opinion on the mod team is that we want you to apply common sense. It doesn't need to be graphic to get the point across. If you're concerned it crosses a line, contact us and ask us to check for you. Or post it anyway and see what happens - the worst we're going to do is to ask you to either take it down and post it elsewhere, or tone things down a bit.