The Piped bot is checking comments for instances of a YouTube domain and video id (I don’t know specifically what it triggers on) and then replies with a link to that video id as a Piped-based one. But what it should also do is check if the initial comment also contains the Piped URL it’s about to post and then not reply with a duplicate of that same address.

For example I’d post something like

• Watch this YouTube video (Piped mirror)

And the bot would reply offering the exact “Piped mirror” address I had already linked to. This would happen regardless of if I used custom link text or just left it as a raw URL so the bot clearly wasn’t doing a check of either method.