Ok so for all my fellow ignorants, if anyone wants to verify their Carrd link for their Mastodon Bio (you know, make it nice and green just because):
The way to do it is to add the link to your mastodon inside carrd (be it link, or button option) just REGULARLY, starting from https and THE ONLY THING you add at the end is:
||me
THAT then translates to "rel='me" in the html, which is what mastodon looks for. Thats it, its just a very specific format nobody mentions.
