Microsoft Bing is testing bolding the site name in the search results snippet when you hover your mouse cursor over the search result snippet. This is similar to Bing bolding the title on hover, but in this case, it is the site name.
This was spotted by Sachin Patel who posted an example of this on X - I was able to replicate this, so here is my GIF:
How bold of Bing!
Forum discussion at X .
