Had this question in mind. IIRC your Page Rank(PR) increases whenever you get a backlink from a popular high PR site. Will my site's PR increase if I , say , include it in my signature/make a post with it/include it in my profile?
this can work as a off page seo optimization up to a certain point, but spamming your domain in a profile signature can also lead to downranking your site over time. keep in mind that the google algorithm is grdually becoming smarter. (I assume you're seo optimizing for google.)
additionally the importance/weight of fora backlinks for serp positioning has been decreased over the last years. however, if google discovers a thematic relation between the forum you use for advertisement and the domain in the signature, you will gain some backlink power.
tl;dr there is no clear answer to this question - it depends.
