Due to the new enhanced copy-paste handling, the URL would be included in the user’s reply as code, too! By surrounding the link in angle brackets, we prevent the bot from accidentally including the link itself and spoiling the surprise.
I considered having the bot automatically edit the user’s post to remove the backticks. I very quickly ran into a problem with spurious whitespace, and it would also look super weird for the bot to edit your post when that’s not what’s being taught. The seemingly bare link not automatically embedding is also weird, but slightly less so.
Fun fact: this doesn’t work on localhost, because the onebox engine refuses to issue requests to localhost
Note: this change will need to percolate to translations, but let’s let that happen naturally.