Adopted by the Journal of Cheminformatics (Aug 2020)

Adoption announced, editorial by Egon Willighagen
Blog post by Willighagen on the same subject
CiTO updates (another blog post by WIllighagen)

BioMedCentral on the CiTO Pilot (seems to only include Journal of Cheminformatics, for now).

What about adoption by tools?

Willighagen offers rudimental instructions for BibTeX (but probably only suitable for Journal of Cheminformatics at the moment) as well as for Google Docs + Zotero (not really working) in this github repo.

Markdown template with CiTO for the Journal of Cheminformatics.

The best tool with support for CiTO: pandoc scholar

Pandoc Scholar appears to be our best bet at the moment if we want to use CiTO in our manuscripts.

Krewinkel A, Winkler R. 2017. Formatting Open Science: agilely creating multiple document formats for academic manuscripts with Pandoc Scholar. PeerJ Computer Science 3:e112 https://doi.org/10.7717/peerj-cs.112

Other notes

It looks like support for CiTO should happen at the document processing tool stage, and not in our reference managers (Zotero, etc.).
I wonder if something like Biber/BibLaTeX should add support for CiTO, or if that's the wrong abstraction level.

Martin Fenner has a blog post from 2011 (Google Cache) where he shows how to use CiTO with a Wordpress plugin, unfortunately both the post and the plugin appear to have gone offline.