(It's a stupid rule, I think. And your idea is a good example of why. For another, imagine such a rule on, say, YouTube. Why shouldn't a single account's Reddit posts be considered as a kind of channel?)
Feel free to post links to your own content (within reason). But if that's all you ever post, or it always seems to get voted down, take a good hard look in the mirror — you just might be a spammer. A widely used rule of thumb is the 9:1 ratio, i.e. only 1 out of every 10 of your submissions should be your own content.
Make sure you're in an appropriate subreddit and be transparent and you should be fine.
In any case, I would still say that the "if that's all you ever post" note is silly. It deprives Reddit of the channel idea, which would be a good addition, I think. (If people don't like your stuff, then they can downvote it.)