I'm only going to say this once: everyone is free to discuss potential alternatives to the rules, but rehashing or challenging past warnings should be left to report tickets or PMs; furthermore, attacking each other is off-limits. Handle your personal grievances elsewhere, hopefully in a productive manner.
For the time being, I'm leaving some of the questionable posts in place. If it comes to my attention that members are fighting again, then expect punitive action. Strong opinions are no excuse for poor conduct.
The difficulty with setting out strict guidelines for Borderline NSFW content is that such content does not always have a clear marker. People often have different standards of what is acceptable, borderline, or an outright violation of decency; thus I'm disinclined to believe a strict definition, if it were possible to render, would settle the matter beyond dispute. There would always be the potential for a case in which a final definition could not effectively cover, and a judgment would need to be made on the spot.
The best answer I can provide at present is this: Borderline NSFW comprises content which is made in poor taste and is inappropriate for general audiences. Someone might consider "Grammar Nazi" inappropriate, as it makes a comparison to a deplorable regime; on the other hand, general consensus -- and this where things get fuzzy -- is that the phrase is doesn't raise any offensive red flags in and of itself. If one were to start posting pictures of ponified Hitler, however, that would constitute inappropriate content. Posting photographs of corpses from concentration camps or mutilated animals would likely net a full NSFW warning.
In the end, though, we're caught between a rock and hard place. Someone might just find ponified Hitler funny and therefore not inappropriate. And posting lists of examples would invariably leave gaps for people question. ("Why is X subject considered borderline when Y is allowed?") Here we tread into the need for interpretation -- and though the current staff is far from perfect, its deliberations are rarely if ever made in undo haste.
Generally speaking, a member will receive a PM about such content, unless said content is considered outright NSFW or if the member in question has a history of ignoring the rules. We also have PMs and the support ticket system. These are the fail-safes designed to help prevent difficult cases from going unaddressed.
Finally, even if you are upset with the current rules, please be respectful. It appears to be far too easy for someone to assume the staff is composed of soulless automatons who would like nothing better than to punish people. We really don't enjoy pestering people via PM or handing out warning points. Getting snarky with us only muddies the waters and undermines your position. We're not asking folks to get obsequious and butter us up with niceties -- but it's no fun reading through responses that effectively assert how wrong we are because we don't know how to enforce our own rules.