A mod can ban you from their subreddit and that happens a lot based on a fairly subjective basis. There are even times where you just get caught by moderating bots then if the moderators don't bother to reply to you, there is little recourse. I have heard of cases from friends who have been banned for fairly bizarre reasons. I'm not saying you will be banned the first time you break the rule but people who post about content they create have to be extremely careful or they can be banned either from a subreddit or globally. When you are a moderator of a subreddit that has millions of viewers, I think it shouldn't be so subjective.