What would be the purpose of/reason for moving back to a different url? If its been a few years, I’d leave it alone unless you watched everything decline since moving to the main url. Moving the forum to a new url now would probably be a bit chaotic, not only for your main url but for the forum itself…. Only reason I could imagine myself moving the forum in this scenario would be if all those links were really awful and unrelated to the url it currently sits on…
The SERP is the front-end to Google's multi-billion dollar consumer research machine. They know what searchers want. In this data-heavy talk, Rob will teach you how to uncover what Google already knows about what web searchers are looking for. Using this knowledge, you can deliver the right content to the right searchers at the right time, every time.
Since heading tags typically make text contained in them larger than normal text on the page, this is a visual cue to users that this text is important and could help them understand something about the type of content underneath the heading text. Multiple heading sizes used in order create a hierarchical structure for your content, making it easier for users to navigate through your document.
While Google is on record as stating these quality raters do not directly influence where you rank (without more senior analysts making a call on the quality of your website, I presume?) – there are some things in this document, mostly of a user experience nature (UX) that all search engine optimisers and Webmasters of any kind should note going forward.
At first glance, the Ads or SC appear to be MC. Some users may interact with Ads or SC, believing that the Ads or SC is the MC.Ads appear to be SC (links) where the user would expect that clicking the link will take them to another page within the same website, but actually take them to a different website. Some users may feel surprised or confused when clicking SC or links that go to a page on a completely different website.
QUOTE: “Some pages load with content created by the webmaster, but have an error message or are missing MC. Pages may lack MC for various reasons. Sometimes, the page is “broken” and the content does not load properly or at all. Sometimes, the content is no longer available and the page displays an error message with this information. Many websites have a few “broken” or non-functioning pages. This is normal, and those individual non-functioning or broken pages on an otherwise maintained site should be rated Low quality. This is true even if other pages on the website are overall High or Highest quality.” Google

Make it as easy as possible for users to go from general content to the more specific content they want on your site. Add navigation pages when it makes sense and effectively work these into your internal link structure. Make sure all of the pages on your site are reachable through links, and that they don't require an internal "search" functionality to be found. Link to related pages, where appropriate, to allow users to discover similar content.
In 2007, Google announced a campaign against paid links that transfer PageRank.[30] On June 15, 2009, Google disclosed that they had taken measures to mitigate the effects of PageRank sculpting by use of the nofollow attribute on links. Matt Cutts, a well-known software engineer at Google, announced that Google Bot would no longer treat any nofollow links, in the same way, to prevent SEO service providers from using nofollow for PageRank sculpting.[31] As a result of this change the usage of nofollow led to evaporation of PageRank. In order to avoid the above, SEO engineers developed alternative techniques that replace nofollowed tags with obfuscated JavaScript and thus permit PageRank sculpting. Additionally several solutions have been suggested that include the usage of iframes, Flash and JavaScript.[32]

There are a lot of definitions of SEO (spelled Search engine optimisation in the UK, Australia and New Zealand, or search engine optimization in the United States and Canada) but organic SEO in 2019 is still mostly about getting free traffic from Google, the most popular search engine in the world (and almost the only game in town in the UK in 2019):
In the last year, Google and Bing have both indicated a shift to entity-based search results as part of their evolution. Google has unscored this point with rich snippets and Knowledge Graph, and Bing has now upped the ante on personal search results with Bing Snapshots. Find out how you can adopt strategies to stay ahead of the curve in the new world of semantic search results.