I'm in 100% agreement with that. Permitting users who are required to make disclosure to include them in signatures and profiles has been perverted (by some) into free advertising space.
(P.S. - I'm on the record if being against ANY signatures.)
Thinking out loud...
Mark their posts and profile with an icon that they have a legal disclosure, and link the icon to their disclosure page. We should probably allow links to their site(s) and legal disclosure(s) on that page, and maintain an edit history. We should also provide room for any disclosures they want to make in case they don't have a site to refer to. It will be up to the individual user to maintain the content of their disclosure page. I think it should be pretty generic - links and text - no advertising. Or, perhaps allow some banner advertisements for an additional fee.
Any post (or PM) made while their account's IRP status is in good standing wall carry that icon perpetually. The burden will be on the user to ensure their IRP status is maintained if they are posting about stocks that require disclosure. Failure to do so will fall under the purview of the appropriate regulatory agencies, and we cooperate with those agencies. If in our judgment someone is posting about companies they are promoting while failing to disclose their IRP status we can always cut off their water.