Hi Jeremy, hi Emilio, You're right, the tidy-html5 source package is meant to replace the tidy source package. I'm sorry for not following the correct procedure there; this is my first attempt to update an orphaned package.
This new version is a major update but not a rewrite, as I understand it. The upstream name changed, and also the soname of the library. I'm currently preparing a packaging update to address #827891 #827716 and several other bugs. Cheers! Daniel