In the past, some Opera employees do have commit access to Blink. When I was working on the content layer of Chromium (and some other parts) as an Opera employee I never had commit access, though I do get bug editing access (which is for triaging bugs).
Overall, it doesn't feel like there is a community at all, it's more like Google deciding everything then tell external contributors as a courtesy. I believe there can be technical influences driven by non-Google contributors but that's pretty rare.
That said, perhaps Microsoft can be an exception if their participation is big enough.
> This project began by pulling the original “Helvetica” font from my system files, and making a copy of it. From there I opened it in FontForge, which is a brilliant open source font editor.
Pretty sure the license won’t allow you to do any modification to the font installed on your system.