There is a method of forum spamming that’s been making the rounds for the past few years, it’s called Profile Builder Forum Spam. The idea is to circumvent getting banned for posting links to forum discussions. The way the forum spammers do it is by creating a member profile at a forum then making numerous posts, often to older discussions that have been around awhile. The idea is that the member name contains a link back to the member’s profile and that some link equity will flow from the discussion post to the profile and to the link to their site that is on that profile.
The nofollow question
Nofollow/Dofollow doesn’t generally matter. Link monkeys doing profile building on behalf of a client are not detail focused. They’re sloppy. They’re just required to do one thing all day. So I don’t believe they’re checking for nofollow. Beyond that there are a group of link builders for whom it is convenient to sell their clients the idea that nofollowed links work for ranking. This is a common myth that persists because it makes it easier to sell easy to acquire low-quality links. They use arguments such as it’s hard to imagine Google would ignore so many links, that nofollowed links still have value in their anchor text and other non-hyperlink ranking factors. Others claim that having a mix of dofollow and nofollow links will help your spammy link profile look natural.
Profile builder profile
There are different kinds. Some are cut and paste (they Google the OPs question and select an answer from the top three of the SERPs). Many are echo posts that restate what has already been posted. Then there are fluff posts where they thank the members for posting the info, or some such useless post. Non-U.S. and non-European profile builders are generally not chatty. They are usually in a hurry and tend to make a flurry of posts in a single day.
U.S. based forum spammers are often a little different and I haven’t seen them engaging in profile building. Their method tends to lean toward a naive style of self-promotion along the lines of an introduction plus a link to their own site. They then follow up with chatty responses in other posts. These aren’t really done for profile building purposes though. These are for signature link type links. These folks are usually some small business person who read a post somewhere that posting to forums is a good way to promote your site.
Your forum no-follows all links, so why should you care?
Over the long term, I believe a website, any website, stands or falls according to the quality of it’s content. Profile link builders tend to post copied content (can be a negative signal to search algorithms) and fluff (a negative experience to your forum members). Both affect the perception of quality and usefulness of a forum, as well as possibly negatively affect your search rankings either directly or indirectly because of reticence of others from linking to a site that hosts poor content. As a forum administrator, it should be your mission to curate the best possible experience for your members. Search rankings often follow as a consequence. If you aren’t aware of this kind of spam then moving forward it will be useful to be on the lookout for profile builder spammers.