One of Stack Overflow questions has a self-answer inside the question and I wanted to add a comment about ability to self-answer and tried to find relevant links by searching within Stack Overflow. The search results returned were obviously about software, not what I wanted to get. Then I did the Google search “stackoverflow.com self answer help” and found the links that I wanted.
Why should Stack Overflow users have to use external search to find answers within Stack Exchange?
It will be nice to have an ability to include in search results help topics and FAQ questions from the site’s meta and global Stack Exchange meta (with help or meta FAQ tags respectively). (Additionally, it will help to increase new users awareness about SE rules and etiquette.) I want to highlight, that I am suggesting to include in the site search results not all meta content, but only FAQ articles FAQ Index for Stack Overflow and FAQ for Stack Exchange sites
It can be done by default, have an additional checkbox in search or may be suggested how to do it in ‘Advanced search tips’.
My suggestion may be considered as a duplicate of the old Include meta in search results and related questions? feature request, but 11 years later SE may have different opinion how it could be addressed.
Jeff Atwood in 2009 said that “cross-site related queries is far beyond the scope of anything we'll be able to do anytime soon.”
As pointed by Rubén in the comment, cross-site search is already available on stackexchange.com, so there isn't any technical limitation to do it.
To include topics about a site in the site search will make the sites more new user friendly, which is a priority of the current Stack Exchange network.