How do you interpret vague rules like "Don't be a jerk" in context?

Many subreddits include rules written in informal language — "Don't be a jerk," "Be excellent to each other," "No toxic behavior" — that communicate a general norm but provide little specific guidance about where the line actually falls. Interpreting these rules requires attention to context and a degree of judgment that more specific rules do not demand. The first step is to treat vague rules as revealing the community's default tone rather than its specific prohibitions. A rule that says "be kind" signals that moderators in that community will err on the side of enforcing civility and will remove comments that feel aggressive or dismissive even if they do not contain explicit slurs or threats. The existence of such a rule tells you that the community has historically needed to address incivility, and that moderators take community tone seriously enough to codify it loosely. In that context, borderline comments that would be uncontroversial in a subreddit without such rules may get removed. The second step is to read the recent comment section of popular posts to calibrate what the actual community behavior looks like in practice. Vague rules are enforced by human moderators who have a sense of what "too harsh" looks like in their specific community. Observing how moderators have handled previous threads — which types of comments they left standing, which ones they removed, whether there are stickied moderator comments clarifying expectations — gives you a much better working model of the rule's scope than the text itself. When genuinely uncertain whether a comment you want to make falls within "Don't be a jerk," the useful heuristic is to ask whether the comment criticizes a position, idea, or piece of content, or whether it criticizes the person who holds it. Most vague civility rules draw the line there: substantive critique of ideas is generally protected; personal attacks on people are not, even when expressed mildly.