In other words, it's subjective and self-reinforcing?
Of course its subjective. It's impossible to define every situation and appropriate responses. If that were the case, we could have robot mods, and just automate the process.
Written words do have intent. If the intent appears to be crossing the line of what has been defined as part of the TOS, there may be discussion among the moderators as to appropriate action.
If someone says, "Hey jerk... go screw yourself." that's easy to moderate.
Other times, it's more vague as to what the user meant.
However... If we have users who require habitual moderation, the recurring patters of language, attitude, intent are assumed.
There have also been members who have been banned, simply because they require too much attention from the moderators. I won't name names of anyone, but certain users just have to be voted off the island for the greater good. Mods are volunteers, and devote a lot of time to helping to keep SB a civil and fun place. If one user is consuming so much of a volunteers free time, then from my perspective, that user has reached the point of diminishing returns, and it causes the moderator to resent even being a mod because they're not having fun, they're just being cops.