Ask HN: What is the thin vertical green line in these search results?

When I perform this search: https://www.google.com/search?hl=en&q=why%20do%20characters%20with%20accents%20look%20like%20gibberish%20characters

There's a thin vertical green line in the search results (you might need to scroll down a bit). The behavior is persistent across browsers, private window or not. Is this a bug with Google? Can anyone explain what the cause is? I'm really curious.