Great post overall. I did some tweaking in my suggestions and used some Grammarly to help. Feel free to accept or pass on any of them 👍

Pretty good! Or, to use typical High French Praise: "not bad". I left a bunch of minor comments, but two things:

1. These blog posts always need a closing call to action. "Mainmatter's Ember Initiative aims to improve Ember for the entire web. We need your support: talk to your employer about sponsoring our effort, spread the word, and follow our progress on this blog. You can get in touch with us" etc.
2. I'm not too sure what the goal of this blog post is between:
   • announcing the codemod (great for Ember developers on a recent version who want to upgrade to Vite)
   • explaining what this codemod does and how to use it
   • explaining how this codemod works and how you approached it (and future versions)
   • explaining what codemods are and how to write one for a different problem

You could state clearly in the intro "we are excited to release this codemod, which will make it easier to upgrade to Vite, and we're going to explain what it does and how you can use it" for instance. This is just my opinion, but it feels like it needs some focus one one (maybe two) of these threads