I am aware of this questions: Transparent FavIcon in chrome
It does not solve the issue.
On this site the icon for the SharePoint.stackexchange.com appears with a black background. For example on my profile page
But on other sites in the Stack Exchange network the black background of the icon is not showing and the icon is hard to recognize. Here is the icon in my profile on StackOverflow
I don't know what exactly is going on there, but I feel it is a bug. The SharePoint site icon is hardly distinguishable on any other Stack Exchange sites. The black background that helps identify the icon is not visible in other SE sites.
Edit: on the SuperUser site, the SharePoint site icon shows correctly with a black background.
How come the icon does not show consistently across all sites in the Stack Exchange network?