signature campaigns are use to introduce or advertise the upcoming projects or ICO, im sure while you reading all the folks comments in this thread, you can see some of the advertisement under their comment, thats the signature campaign and they are  participating on that campaign to be paid in, its either BTC or TOKEN. wearing that signature code are a profs that you are in campaign, but before you apply on any signature campaign you have to do is reads the rules from the first page and took if you are eligible because some of campaigns now are not accepting newbie-member rank, they are accepting Full Member up, so unluckily both of us are not eligible to join/participate in any campaigns, but theres a few campaigns that really accepting jr - member rank and they are rare.