Original comment from @SCP-2000 :
Include a link to the spam-blacklist false positive reporting page (e.g. en:MediaWiki_talk:Spam-blacklist) in the warning message when users attempt to link to a blocked domain. If possible, the community can customize the link, and even the entire interface message.
The messages are currently:
// link inspector: "visualeditor-linkinspector-invalid-blocked": "People at this wiki decided to block links to this site. Please try another link.",` // citoid: "citoid-citoiddialog-reliability-unreliable-title": "This site is blocked", "citoid-citoiddialog-reliability-unreliable-description": "This source is considered unreliable by our community, and therefore is not allowed. Please choose a different reliable source.",
It's sort of complicated where to link to in the completely generic messages that're supposed to work for all projects / third-parties, because there's not some automatic page on every local wiki that works for it. Maybe https://meta.wikimedia.org/wiki/Spam_blacklist/About? (It's a better introduction than the en:MediaWiki_talk:Spam-blacklist page for a random new user, though admittedly less immediately actionable.)
That metawiki introduction page is only for the global spam blacklist, rather than local spam blacklist. So it may not be a good idea to link to that page. Perhaps create a FAQ page on mediawiki.org, to redirect users to different wiki reporting pages (I wrote a draft of the FAQ page for reference)? Thanks.