That was my bad, sorry for the confusion. You should see full logos in chat again for sites that have custom designs. Sites that are using the shared default site design will still have the icon only.
First, some background. All Q&A sites and styles follow the same pattern in terms of the assets they need and where they are located. One of those assets is
logo.png and over the years it has been almost entirely deprecated. The sites themselves have switched over to serving
logo.svg for sites that have a custom design or rendering the site name in text for sites that don't. The only remaining uses of
logo.png were in chat and in email templates.
A couple weeks ago I deployed a change that removed the dependency on
logo.png from the email templates. I then removed all
logo.png files for sites that don't have a custom design... and discovered that the API provides
logo_url as part of the Site object. No problem, I thought - I'll just add a fallback to serve the
logo_url is unavailable.
In hindsight, this is obvious, but the API project doesn't have access to the same file system location as Q&A, so basically it considered all logos unavailable. :) Chat fetches the site list from the API, so that's how we got to replacing logos with icons.
apple-touch-icon is just a filename. I don't know if it has origins in something Apple-specific, but at the moment for us it's synonymous with "the site's icon" across all devices.)
Okay, but really, why now?
We're building more tools to empower the CM team to handle parts of the site lifecycle that previously required a developer. One of those tools is automating the removal of the "public beta" status. So we built a shiny new tool that allows a CM to "graduate" potentially multiple sites at the same time. With the logos in place, they'd also need to edit them themselves to remove the word "beta" or coordinate with someone in design... and that's more overhead than necessary for images that are barely even used, as I mentioned above.
We want to keep moving away from
logo.png. The next steps here are likely to make chat grab and display SVG versions instead and improve the treatment that sites without a custom design get. The API may start pointing at SVGs as well, though we'll still need some sort of fallback for sites without a custom design.