It works here, on Discourse Meta, just not on my instance (https://forum.appleseedhq.net). It’s more of a slight annoyance than anything else, but it makes it hard to spot the Discourse tab in the middle of many other tabs.
- On all browsers: Everything appears to work fine when ‘Topic count on browser icon’ is disabled.
- IE 11: The favicon appears but it doesn’t carry any topic count.
In pictures, with ‘Topic count on browser icon’ enabled (look at icon in tab):