Advertising another RP site in your [i]signature[/i] is not against the rules. It's making a whole thread to advertise (or I suppose even just a single post) - that sort of thing. In fact, iirc, "either put a link in your signature or just stop advertising altogether" is usually what the mods say to people who try to advertise (or at least, the ones that are clearly still members of the community and not just here for the sole purpose of advertising).