A signature is a kind of passive feature that does not presume anything bad in my opinion, as long as your posts are aimed at contributing to the forum, and not at quick responses to cover the signature campaign posting requirements. If the posts are ok, then the signature does not conform an issue.

Social bounties on the other hand very often clog one’s posting history, standing out, and tend to define a profile as you say of a non-contributive forum member. Those I believe should probably avoided if possible.