No matter what favicon you customize for your blog on a separate domain,
yourcustomdomain.com/favicon.ico always throws the default write.as favicon (which is also indexed by google).
I checked on multiple devices and browsers to make sure it wasn’t a cache issue and it’s definitely a bug.
This is by design, so all Write.as sites at least have a default icon.
With custom favicons, the way it works is that we point to your icon with a <link rel="shortcut icon"> tag in the header. According to Google’s documentation, they respect this and use the defined icon in search results.
However it does say that favicons should live at a stable URL, which doesn’t happen with our current setup, and might cause problems. But I’ll need some time to figure out how we might work around this. Due to how we’re set up, it wouldn’t be a quick fix to always make your custom icon live at yourdomain.com/favicon.ico.
In the meantime, you could try asking Google to re-crawl your site, and see if that updates the favicon for you. If that helps, please let me know!
Are you using Write.as or Write Freely? I’m on Write.as with a custom domain, and my favicon works as expected in browsers and search results. If that’s what you’re using, just upload your custom icon into the built-in favicon setting in customization.