On the hot network questions page, site icons are showing 48px versions in 32px sizes:
I know there are 32px versions because I recently posted another bug report and looked through all of them.
If you replace 48 with 32 in img src, everything will look fine:
As of June 2018 this bug is still not fixed. So I posted my own fix on StackApps: StackExchange Hot Network Questions page icon size fix