PSA: If you share a YouTube video using the native share feature it now attaches your user ID (?si=xxxxxx) to the URL automatically.

YT likely does this to growth-hack DMs. When someone clicks on the link, YT can start a DM thread between you two automatically with this ID even if they found the link outside of the YT app.

If you post links publicly, I strongly recommend deleting the ID unless you want to post your user profile.