gbaz
This is an issue with hscolour, which is used by haddock: https://hackage.haskell.org/package/hscolour it currently does not have an active source repo, much less an issue tracker, but you should probably...
Indeed, the hackage search covers package names and descriptions, _not_ readme files, which is where that text appears.
I believe that this is because the docbuilder is still partially stuck with using cabal v1-build, which can't support them. cf https://github.com/haskell/hackage-server/issues/821