Couple of questions;
Do not double post in a single topic, cross-post between boards, or bump an older topic.
What might cross-posting be?
...and ensure that your signature is no larger than your average post.
Hmm, I think most will find that quite hard. Most people who have quite large signatures tend to stick to one or two line posts, and most people who write relatively long posts tend to know better than to support tons of projects. I'm not saying this rule is unneeded, just that for that some people will end up with rather short signatures.
Actually it would be quite good if you made a thing calculate the average length of a users post, and limit their signature to that many characters.... just a thought.