Microsoft is testing, showing a notice at the bottom of the Bing search results that says, "Search by typing anything on the keyboard." This happens when you reach the footer of the Bing Search results. When you start typing, your characters appear in the search box for a new Bing Search session.
Frank Sandtmann posted about this on Mastodon, I cannot replicate it for some reason, but he said, "Bing may be running another user interface test: as soon as you reach the bottom of a SERP, a notice appears on dark background. It says: "Search by typing anything on the keyboard" and takes you right back to the search box."
Here is his screenshot:
He explained Google does something slightly different and asked, "I wonder how many searchers actually use such features..."
Forum discussion at Mastodon.