When the owner of a website is described as committing off-site SEO, that usually means that they are spreading awareness of their website across various outlets on the Internet and nurturing their social media profiles. The strongest indication that their off-site SEO campaigns are working is that other websites, primarily those that focus on the same industry or topic, are posting backlinks that direct their own audiences toward the website. If the other websites are voluntarily linking to a given website because they deem it to be a valuable resource worth sharing, they will opt to exclude a piece of syntax called "nofollow" so that Google will not overlook the backlink's relevance as an indicator that the website's value is being recognized by its peers.
Getting a backlink to appear on a website without resorting to black hat methods is seen as something of an art form because it tests the website owner's integrity and capacity to effectively put that integrity on display. There are many black hat ways to force backlinks to appear out of the website's domain without them coming about naturally, but Google is only ever becoming more accomplished at seeing these tactics for what they are and penalizing the website's rankings on SERPs.
The simplicity of including backlinks in posts made on other websites' public forums means that they are equally likely to be posted by either webmasters engaging in black hat tactics or well-meaning commenters who are sincerely impressed with a particular website. Therefore, Google technically does not penalize websites for backlinks appearing on other forums, but it does not award them anywhere near as much ranking credit for those as it does for backlinks posted on websites' blog features. The primary incentive for a well-meaning webmaster to create self-promoting forum posts with backlinks would be to establish points at which Internet users in general can be casually referred to the website without them feeling like they have been directed to do so by a marketing campaign. This organic spread of awareness should allow audiences to naturally gravitate toward the website out of curiosity. For more information click here https://www.reddit.com/r/SEO/comments/baif2h/isforumpostingworkingnowinseo/.