Most signatures seem to be promoting a WSO or an IM offer. Of course, this makes sense on an internet marketing forum.
However, if you don't have an internet marketing offer at the moment, are you allowed to link to another domain you own - one of your "money" sites?
I don't see anything in the forum rules against it, but I just never really see signatures with links to dieting sites, train your pet sites, etc.
Do you not link to your Adsense/content/money sites in your signature because you think the sites will not catch the interest of the members here, because you don't want people to copy your money sites, or because it is against the rules in some way.