that's not how you link communities on lemmy, c/whatever means absolutely nothing since you're not specifying the server, it's like telling me to send an email to dave@
I know, it doesnt have a meaning but we can give it one, my meaning is that c/community means a community in the instance that the post was posted. Having to put 4 brackets a name and a full link with https:// is too long if is in the same instance