We have already logic that references in a list cover the preceding paragraph, under that assumption that it is just an introduction to the list and doesn't need referencing itself.
The same should apply to blockquotes, as seen here:
https://en.wikipedia.org/wiki/Mnesarchus_of_Athens
Tables as well? I was thinking that we might want to generalize it out to any non-paragraph node that follows a paragraph, but then I was thinking of things like an image-caption that'd qualify but really shouldn't count.
Change #1240237 had a related patch set uploaded (by Esanders; author: Esanders):
[mediawiki/extensions/VisualEditor@master] AddReferenceEditCheck: Detect refs in sibling blockquotes and tables
Change #1240237 merged by jenkins-bot:
[mediawiki/extensions/VisualEditor@master] AddReferenceEditCheck: Detect refs in sibling blockquotes and tables