Restrict the bot from processing previews if it is itself the author of a message.
This may be achieved either using a command check, or placed directly in the preview message handler.
It is unclear if the a command check is flexible enough to achieve this. It is meant to take only the context of the command as input. However, the bot's user ID is a property off the
bot
object. There doesn't appear to be a built-in decorator to check for this case, either.
Fixed in v0.8.5 and deployed to production.