In some older systems I’ve used, you could auto-link to another card just by typing its ID, like “See #123 for more info”, and “#123” would be a link to card 123. For Infinity to do this, I think you’d need two things:
display a card ID on each card
enable auto-linking (maybe based on regex?)
Note that auto-linking could be used to tie to github or any other system too, if you make it flexible: “github#123” could link to our github issue #123 (etc.)