I am member of several forums, some active some not. I joined but had not been active on this forum due to time constraint.
Here's what I have noticed. The forums who are strict about promotions other than specifically allotted promotional threads, but generous with signatures, in terms of space and links, are doing much much better. The reason is simple, signatures do not interfere with the message as much as text of message.
The reader can easily ignore the signature, unless he/she finds information of interest.
Kindle boards, mobileread is a good example. Just something worth consideration by the administration. Thanks.